I don't think these should be allowed, or possibly just downvoted. Getting information from the forums is fine, but copy+pasting (especially without bothering to format) is bad. What often happens is that a series of posts are copied, which is not a good format for answers. Answers should get straight to the point rather than being a conversation.
Bad:
Bobjoe520 said: Why do we do the thing with the stuff?
JoeBob said: because it's better that way.
Bobjoe530 said: but why is it better?
BobExpert said: It's better because the foo of the bar and complicated explanation.
Good:
From http://example.com/forumpost:
It's better because the foo of the bar and complicated explanation
— BobExpert
Better:
The reason why the foo of the bar is because the bar of the foo is barry of the fooing <complicated explanation>
More info here: http://example.com/forumpost
The key point I'm trying to make for "better" is to read and then re-word the post to answer the question in stackexchange style and to directly answer the question.