Clarification on the doujin rule

I am confused on what the rule is, I heard that while it is a rule, it is one that is violated constantly.

Should I ask a site moderator first before I plan to upload one to see if it would be approved, or is there going to be a change soon that will make official the ban since currently it seems like artists with doujins already uploaded are pretty likely to have new ones uploaded. I can see why people would say, "post it on voile" but currently, a fair amount of doujin there have been posted here, and the translation here is used as a base for works there, and vice versa.

I understand that some artists don't want their work uploaded here, period, but I'm not sure if the rule is actually enforced for all doujin.

Just see forum #45499. The policy hasn't changed, and likely isn't going to change.

Basically, if you can get away with it, good for you, but don't expect it and don't cry if your approval ratio suffers. Each page will be judged on its own merit, Danbooru has no fetish for completeness. So it's not really the best place for it. And it's definitely not a good way to get a high approval ratio.

For one thing, black and white pics seem to be less likely to get approved. And one tip, when considering an artist who has some doujinshi posted here, check which ones of his doujinshi haven't been posted. There might be a reason.

In the TOS look under Prohibited Content.

There's always been a rule in place, albeit one that hasn't always been strongly enforced, but some mods are now trying to filter out commercial doujins. There's no hard ban against them right now, though.

Commercial manga are not allowed, full stop.

Uploading a full-sized doujinshi is generally not encouraged,* but uploading just a few especially good pages should be fine.

Uploading web-original doujinshi (e.g. Chibi Miku-san, or various stuff that originated on artists' own web sites) is fine, as long as it meets quality standards.

(*) Note: this mostly means that we don't want Danbooru to become a dumping ground for the latest Comiket releases.

This is how I understand it to be.

The most widely accepted sequential art form uploads at the moment would be ongoing, freely web-accessible webcomics such as Minami's Chibi Miku-san (as sgc mentioned).

Everything else I try to give a pass on. Even when I really like it. There was some K-ON! doujin recently that I really, really liked and wanted to approve but didn't because I don't want to encourage the practice.