What Retrobike "feature" do you avoid when looking for bikes?

Any bike that has a "clever" Adaptation to make incompatible gear shifting compatible - in the mind of the owner and nowhere else
That would really depend on the price of the bike, how much I want the frame and how much needs changing. In a lot of cases I'd rather wait for a bare frame to come up and do it my way from the start. Not being left with stuff I don't want and then have the hassle of selling on/disposing of.

This is exactly why I tend to buy more frames than complete bikes nowadays…More expensive in the long run…But it’s only money 🤷🏻‍♂️🤦🏻‍♂️🤣