There is little grey area here. These things are all common sense and a matter of good etiquette and courtesy.

Guidance on this has been written multiple times. It is up to people to find and educate themselves.

If you don't get it you shouldn't post anything until you do. Just a few examples would be:

Posting unrelated links is spam. Asking for upvotes and follows is spam. Copy paste commenting is spam.

These are the same kind of things that are considered spam on other platforms.

I don't buy that people don't get it - they do, they are just hoping that they will get away with it because they can and do on other platforms.