Apart from the security reason raised by Wang Ki Wun, there are other reasons that Overleaf links should not be accepted as replacements for MWEs. (Some of these you mention in your question, but they bear repeating here.)
First, one of the main goals of the whole network is to be a set of self-contained questions and answers. So in the same way that a link-...
I would say, "not as such". It is easy to imagine some support questions ("How do I reset my password?") which are obviously not TeX-related. But a user, especially an inexperienced one, will often have little idea about the source of their problem. They may (wrongly) think they have a TeX problem, when they don't; and they may also wrongly think they have a ...
Don't put links to overleaf in public forum, even read-only links will show your email address to everybody
link from this answer https://tex.stackexchange.com/a/506205/195169
click on share and see the mail (I removed name, but you probably recognise that this is your mail)