I always tape up my bbls. Never had any problems. However when in heavy rain you must be careful as water WILL enter the bbl from the chamber end even if a round is in the chamber. With tape over the muzzle water could collect in the bbl.
I also use to tape up muzzlebreaks, but once when my wife and I were hunting together, I shot a deer with the taped up muzzlegreak. A piece of the tape struck my wife in the face. [She was to my left and behind me].