I think that sort of personality type wouldn't do well in YC selection process anyway. They are unlikely to have many interesting hack stories if they are the s

I think that sort of personality type wouldn't do well in YC selection process anyway. They are unlikely to have many interesting hack stories if they are the sort of person trying to conform. I would guess that such fake co-founders would be spotted and questioned pretty quickly and that this would be a mark against acceptance. But its still a good idea to encourage founders to have a co-founder. They may not listen, but it might be the extra nudge they need.