Plagiarism destroys your reputation, the penalty is an immediate ban of the user. IMHO many newbies tend to plagiarise because they don't read the
rules and guidelines.
There is no reason why someone should need a rule to tell them not to plagiarize. Your argument is akin to saying that people steal because they don't know it is against the law.
Many writers get ideas from other writers, but you cannot copy a chunk of sentences from another writer without being accused of plagiarism. Paraphrasing doesn't help either. Copy and paste isn't wrong but claiming work as your own is.
This is not a new concept. When writing a post if you are writing something that is not your original thoughts and words, you need to cite the author in some way. The forum does not require citations to be made in any specific way.
I don’t quite know where the forum stands on accidental plagiarism.
I would describe "accidental plagiarism" the same way I would describe someone who claims to have accidentally walked out of Target without paying for something: they did something wrong intentionally and claimed it was an accident when they were caught.