the OP doesn't bother me so much, at least traffic is moving in that scenario.
What annoys the sh1t out of me is impatient folk who refuse to merge, and absolutely MUST gain half a car length by slipping up the inside or outside in merging lanes, driving full noise to the very end of merging lanes straight past a long line of cars moving slowly in lane then coming to a complete stop and indicating to merge. Not leaving gaps for side road traffic to come in/out.
The worst one though, is the folk that indicate left to pull into a driveway, slow down and take a sharp right and occupy the entire road just so they can take a more frontal entry into the driveway. Fine if there's nothing around you, f@#king annoying when you aren't aware they're going to do that. Most folk indicate left, pull left , slow down and turn in at least leaving room for anyone behind to continue on past.