Threadhopping with this character?
If necessary, may wish to ask the parties first through PM or ooc comments though.
Backlogging with this character?
Yes
Fourth wall Breakage?
Go for it!
Smutting?
With enough CR potentially. I have no triggers really, though the usual no-gos are in effect (heavy gore, bathroom things, etc)

In character:

Hugging this character?
Yes
Giving this character a kiss?
Yes but he may take it wrong (think it a token of friendship depending on the kiss/situation)
Something more intimate?
If the CR progression heads that way, yes.
Relationships?
He would only have one at a time...?
Punching this character?
Legolas will likely dodge, depending on your character, but you can try/plot with me
Injury?
Sure
Death?
With lots of plotting it is possible :)