I highly doubt you offended him; he might have just overlooked your comment is all. I've made a few posts in groups that got lots of attention, and the huge influx of comments meant that, even if I did read all of them, I didn't react to all of them, and then sometimes I just didn't have the energy to even read them at all. So please try not to agonize over this! I strongly, strongly doubt you offended him.