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.

Here the classes I'd use:

Post, Poster, Thread, OriginalPost, Reply, OriginalPoster, Replier, PostNumber, PostString, PostName, PostDateTime, PostDate PostMonth, PostDay, PostYear, PostTime, PostHour, PostMinute, PostSecond, Board, ImageBoard, TextBoard, BoardText, BoardImage, ImagePixel, PixelRed, PixelBlue, PixelGreen, PixelAlpha, FileName, FileCharacter, PostCharacter, PostInteger, PostPunctuation

I think it's obvious which class would be sub-classes of other ones, and this is assuming you are working with a language that allows inheritance (obvious OriginalPoster and Replier are derivations of Poster).  It's not everything, but will give you a start.