some 2-second later edits below...

Thanks, your code's great. To do what LanX proposed looked to me too scary(=switch to another task and read their manuals, feel free to downvote my human ingredients). And using regex's is too fragile without knowing the full spec of TT, i.e. are nested comments allowed and how to deal with [% and [%#] and [% # inside strings as Corion said. So let TT do it seems the right way to me.

Edit2: To be fair to the regex solutions: it was me who asked for a regex in the first place.