There are a lot of undocumented guidelines that come from discussion in the Database Forum and in staff-only forums which no longer exist.
This is the place to collect all these undocumented guidelines.
Note that this is work in progress, and as these are not Guidelines, you cannot just take whatever is written here as the one and only truth. Use the Database forum to discuss the issues and seek consensus.
Comments by the database manager (nik) or the Discogs founder (teo) carry extra weight. They speak with authority on matters of general policy and intent, database and website capabilities, and expectations of users. Their positions on some issues have changed over time, and they can be influenced by the opinions of users.
TODO: go through the quotes and check context. condense to 1 or 2 quotes.
Only use "none" as a catalog number when the release has no catalog number printed whatsoever. When there's at least one catalog number, and there are more label entities than catalog numbers, the labels without numbers should use the first catalog number in alphabetical order, not "none".
Durations printed on CD releases should not be corrected in the tracklist and explained in the notes (as permitted by RSG § 12.6.5) unless the difference is at least 5 seconds.
Although it is correct to enter durations printed on the release, there are no guidelines for making your own determination of the actual durations, other than that you must obtain the durations from your own copy of the release. Some differences between your measurements and the printed durations are to be expected, since durations can be measured in different ways. For example, it's common for printed durations to only be for the musical content, not counting silent passages between songs, whereas CD players do include the silent passages when reporting track durations (some include the pre-gap as the total track time, some do not). Other considerations include how fractional seconds are rounded, analog playback speed variations when making your own measurements, uncertainty about where a fade-out ends when there's a lot of background noise, and printed durations intentionally omitting intros and fade-outs for the benefit of radio DJs. If unsure about whether a printed duration is "correct", ask in the Database forum.
There is no requirement that double-A-sided releases be entered with "A" and "AA" track positions. If sides are designated on the release, those designations must be used. When sides are not designated, "A" and "B" positions remain standard, even if both sides have the same content.
Additional comment from mjb:
Some (many?) users were in the habit of using "A" and "AA" when the sides were not designated, but the guidelines don't actually support this.
For double-A-side releases (no side seeming to be promoted more than the other), if the sides aren't designated and the content differs, some effort must be made to ascertain which side to call side "A". External sources should be consulted, including charts, official artist/label sites, promotional materials, related releases, and common sense.
Additional comment from mjb:
Some users think the sequence of matrix numbers matters, with the lower number being the "A" side, but this is completely arbitrary; those numbers are normally just chronologically assigned IDs for master recordings or lacquer cuts. They only matter when one has an "A" suffix and the other has a "B" suffix.
Radio promo 7" releases sometimes designate one side as the "plug side", indicating which song is intended to be promoted. Sometimes instead of explicitly using the word "plug", there will just be stars around one of the track titles. The stars are not part of the titles; they're just another way of marking the plug side. These markings can be used, along with the other usual factors, to determine which side to consider the "A" side.
The Promo tag can usually be added to such releases even without explicit "for promotional use only"-type text, although this may be in conflict with RSG § 6.12.2 if the markings are added by means of a stamp rather than being professionally printed on the labels.
Track positions for single-sided releases should still use sides—e.g., the numbers will be A1, A2, A3, etc., even though there's not going to be B1, B2, B3, etc.
See the info above re: Stars around track title.
RSG § 6.12.2 says that a retail release with a promo notice added by means of a stamp, sticker, or "similar" alteration to the cover is not to be considered a separate promo release. It is forbidden to submit such releases as promos, and there is no forum consensus for even adding a release note along the lines of "some copies are gold-stamp promos". Users with such items should simply add the retail release to their collections, wantlists, and for-sale listings, and then use the collection notes, wantlist notes, or for-sale listing description to mention the stamp, sticker, or whatever.
RSG § 6.12.2 says that a retail release with a promo notice added by means of a stamp, sticker, or "similar" alteration to the cover is not to be considered a separate promo release. This also applies to alterations to the media itself, such as when the disc face of a retail CD is altered by means of heat-transfer (silkscreen-like) print overlay.
Many Japanese retail CDs are made into promos by the addition of "Sample" and/or "Loaned" text (often in Japanese characters) on the hub of the disc, along with stickers or stamps on the printed matter. The hub text is not currently considered to be a post-manufacture alteration, so these CDs are OK to submit as separate releases.
When editing a master release (MR), this is the only place on Discogs where you have the option of leaving Submission Notes blank. For just adding one or two stray, unremarkable releases to the MR, that's fine, but if you are making major changes or doing something that other users might not understand, then please mention why you are doing it. Use the Database forum to ask about anything major.
Reissues and remix editions usually belong in the same MR as the original releases, regardless of release date and regardless of variations in release titles, track versions, and B-sides. Likewise, albums released with different titles and track order in different regions usually belong with all the other editions of an album.
The guidelines which apply are 16.2.2 ("Master Release is intended to contain as many releases as reasonable") and 16.2.1 ("[The release] Is a...remix...or other such variation" / "Single including Maxi Single - all versions should be bundled in the Master Release, including Maxi and Remix versions.")
Ask in the Database forum if unsure, because exceptions are sometimes made, per 16.2.1: "Releases shouldn't be forced into a Master Release - if the addition of a release to a MR is contentious, confusing, or difficult, then it should probably not be part of the Master Release in question."
Additional comment from mjb:
If Discogs were to add the ability to have sub-MRs (groupings of releases within an MR), it would go a long way toward reducing the number of arguments about this topic.
Again, ask in the Database forum if unsure.
Some supporting discussion:
Total re-recordings usually belong in a separate Master Release, but partial re-recordings may or may not need to be separate. Use the Database forum to discuss specific cases. It can be said that guideline 16.2.3 applies (if a recording belongs in multiple MRs, don't put it in any of them), but ultimately it comes down to whatever the users decide for a particular example.
Additional comment from mjb:
There is debate over how to distinguish a partial re-recording from a remix with additional production. Sometimes it's just marketing, especially in cases where the artist is billed as "Artist1 vs. Artist2" with producer credits but no explicit remix credit. Some users consider these to be just remixes which belong in the same MR as originals, but others keep them separate, especially if vocals were re-recorded.
The following arose from an old thread where the perceived "clutter" in a release's history was addressed. This would typically occur when one release is merged into another.
Example: Release A is submitted in good faith. It turns out to be a duplicate of existing Release B. Releases A and B are merged (where B is kept), and Release A returns into User A's drafts folder. User edits the draft Release A into something else, creating an entirely unrelated Release C, which is then submitted.
This in itself poses no problem with the database were it not for the fact that Release C's internal history now includes discussions and portions of its original submission history as well as the merge process and disabled images from when it was still Release A. In extreme instances it may even have a sales history (moreso problematic if a physical release is recycled into a digital release).
Clutter aside, users and voters may potentially find the release history confusing. It is therefore advised not to re-use old releases.