Lambda the Ultimate

Is it generally ok to post content with character entity references (like ⇒ for ⇒)? I mean how many people won't be able to read that?

I'd say if you need it, use it, and hopefully anyone who can't see it will say so.

Also, I remember seeing discussion on using "style" tag, but without any conclusion. Could we standardize some style classes by inclusion of their definitions in LtU CSS file(s)?

The LtU CSS files will do this very soon.

I think we need classes for at least quoting previous comments (italic?) and for excerpts (blue italic?

Yes. The <blockquote> element should be used for block quotes, naturally. For inline quotes, I think we'll use the Q element, although I see it's been deprecated/removed in XHTML 2 (but its replacement isn't yet supported by browsers).

should we break tradition to make it different in color from default links?).

I was thinking of using the fairly standard approach of inserting a vertical bar in the margin of a blockquote, which ought to make such quotes unambiguous, regardless of their color. For inline quotes marked up with Q, I think we'll avoid blue.