Requested feature overview description.
Add some words to the site help text that give a short explanation of how e621 works and how it differs from a gallery site.
This might go on the FAQ , uploading guidlines, or maybe even in the red box on the signup page.
The words might be something like:
e621 is an image board, not a gallery site. What this means for you:
All art that is uploaded is immediately visible to everyone, but it must be approved by site staff in order to stay visible. Normally, approval takes up to a few days, but it can be as much as 30 days. If the art is not approved, it will be deleted from the site.
If you upload art you created yourself, it is possible it will be deleted. Usually this is because it is against the rules or does not meet the uploading guidelines. In other words, on e621, you don't have complete control of what happens to your artwork after you upload it.
It's OK to upload art that you didn't personally create or commission, as long as the artist is not on the avoid posting list.
There also used to be some standard-ish help text in one of the forum threads, about uploading your own art. I can't remember if it was a sticky thread, or a "canned" response that staff would give to people that asked. Maybe words from that response would be helpful.
Why would it be useful?
There have been a couple of recent forum threads (one, two) from users who may be unfamiliar with how e621 works, as compared to a gallery site.
Those of us that are old experienced are more likely to be familiar with how a booru/chan/imageboard works. Newer people are probably more familiar with gallery sites (FA and the rest) or "general-purpose" social media (Twitter/X), and may not realize that e621 operates somewhat differently than what they are used to.
Adding a short explanation for new users may help them understand the site better. It may also lower the amount of staff time that is needed to disapprove art and answer "why was my stuff deleted?" questions in the forum.
Arguments against:
This information is kind of already there on various site documents. The "Features" section of the main help page and the uploading guidelines have most of it. It's not all in one place, though, and it tends to be in somewhat long documents.
Nobody ever reads the documentation anyway. :D
What part(s) of the site page(s) are affected?
One ore more of the FAQ , uploading guidlines, or the signup page. Wherever it goes, I think that it's important to be easily visible by new users, and also easy to find later after signing up.