Most Helpful Guy
I don't find any reason of not allowing him, but if he gets needy and tries to talk to you about how things can be changed and blah blah then just remove him afterwards.
Most Helpful Girl
Who cares what your ex thinks? Why are you concerned about what your ex will think of you if you don't follow him? These things should be irrelevant to you. Leave him in the past and move on. I wouldn't bring a ex back into my life again. Not even on Instagram. You are opening a door for things to begin again. It's asking for trouble.