Class Identifiers

Hey /prog/,
If you were to program a BBS similiar to this and wanted to make it object-oriented how would you call the classes? I guess "Reply" would do for any post after the first post. Since you often call the first poster OP (Original Poster) would you call the first post "OriginalPost"? Some suggestions would be great since I'm really bad at making decisions.

The Meme "SICP" is so fucking outdated, give me an answer already or all of you just too stupid? For real, troll on /b/ or somewhere else, but why on /prog/? Really, I thought this was a dececnt please compared to the other boards, seems like I was wrong - stupid shitfucks.