Threadhopping: Please ask me and anyone else involved in the thread beforehand, but usually I don't mind much.
Backtagging: Always! 

Hugging: Go for it!
Kissing: You can try.  
(Something more intimate?): If events in RP happen to lead that way I would prefer to simply fade to black.

Punching: Go for it! Riley'll fight.
Injury: I'd prefer to discuss it beforehand.
Death: I'd rather not.