I've noticed that it's a bit of a hassle having to change the poster of a certain post/topic. My suggestion is that we should be able to change the post and/or topic's author, so if someone leaves the forums and has an important topic, instead of having to repost the topic yet again, a moderator or admin can switch the topic author. It doesn't have to be an important topic, but anything that would need an author switch.
I'd suggest having it under the '?' part of a post, but anywhere will do.

Ethically its incorrect. I am not yet convinced to change authors.
If that thread needs to be having a author name instead of guest, we can just copy the content & then make a new thread.

This can be helpful when someone propose a tutorial.

I'd be voting no, that possibility would leave space to be misused.