I don't know of any category that asks for more than three sentences.
I tend to ask that things brought up in the question be briefly explained in the info, if they are things that people might not know about. So if you ask, oh, "What "gigantic" actor blah blah?" in a question about Robbie Coltrane, I want you to tell us that he played the half-giant Hagrid in the Harry Potter series. If you would prefer not to have to talk about that, don't bring it up in the question. Just leave out "gigantic", and it's fine not to talk about the Hagrid connection.
Almost always, when I ask for more info, it's that type of situation. You tell us the song was a big hit - I want you to tell me if it topped the charts, and which charts, or what kind of sales it had, or who has done cover versions. You tell us a singer died tragically young, I want to know, in one sentence, the circumstances, or what his legacy is. And so on.
If I see paragraphs of info for a question I'm not really interested in, as a player I just don't read it. However, if as a player I'd like to know a little more, and get some context, I can't read it if it's not there.
I play at other websites, and constantly find myself wishing for info sections. "How did King Bagreb die?" they ask, with the answer of "An infected toenail" and I'm all "What? A toenail!? Who is he? When did this happen? What's it all about?" Two or three sentences of info would have helped me satisfy my very real, but actually quite shallow, curiosity. I want to know, but not really badly enough to close that window, open another one, and google him. That work is the question author's job, IMO - pique my interest, and then satisfy it.