There is definitely something going on there - Pate the impersonator (one of the House of B&W assassins maybe?) looking for an Archmaester's key to the Citadel archives, dragonglass candles "working" again, and all around the time of Sam's opportune arrival.
I don't get the impression that it's a red herring at all. In fact, I think this will be a critical piece in the next book, if not the final one. There is a conversation about this going on over at AFoIaF
, particularly with the key and where it may lead.
Be warned, there appears to be a lot of spoiler-filled discussion there - I'm assuming, based on some released transcripts from TWoW.