My situation is of dark mixed pedestrian bike paths or dark narrow streets. The problem is of the light being nearly as bright as for a car but elevated far off the ground. The rider would additionally rise the head when approaching and look at me. At this point I would lose capability of resolving anything on my side, have to slow down and pray that I do not run someone over or end up in a ditch. When you are in a car and someone blinds you with a high beam, you can give them the same medicine and they often react but on a bike you do not have such a recourse. I try to put the hand over my eyes.
On any road wide enough for 2 cars, rumrun6’s point is still valid. The separation between bicycles in that case make the problem you describe minimal unless the rider is a salmon.
However, I avoid riding MUPs at night but not for the reason you put forth. You may have a problem with a helmet light on a MUP but think of what a pedestrian has a problem with. Many pedestrians aren’t using lights and are night adapted. A bicyclists passing with
any kind of light is going to ruin that night adaption for several minutes. In other words, your passing with lights is going to plunge the pedestrian into darkness.
Your “night vision” is ruined because you are running lights. Light from another source may be a bit dazzling but doesn’t have the same effect as going from no light to bright light to no light again.