Slightly different to what is described here, but one of my pet peeves is the "nuclear button" features that devs put in their software - ie easy to activate features that add marginal utility to specific niche workflows but cause irreversible damage to everyone else.

Firefox deleting every single one of your pinned tabs on close if you have a second window open is an example of this, as is YouTube jumping to a different part of the video every time you bump one of the numerical keys on your keyboard.