Does anyone have a comment about how chairs are viewed at retreats, are they allowed?
It depends on where you go. In North America and Europe: I feel that it's generally viewed as sensible here.
Sitting in a chair or seiza will also bring their own issues, so it helps if you take up body-health practices, too, e.g., don't make this relatively new, meditating mind be responsible for the circulatory system in the legs, etc. A good work-out will also focus the mind and help discipline its wandering. The idea here is pervasiveness, but that's a tall order!