Search comments
Often enough to be frustrating, I remember either seeing or making a comment that I'd like to find again -- a helpful reference, a well-written comment that I'd like to use as a template, something involving weaponized unicorns that made me laugh out loud, whatever. If I know who posted it I can painstakingly dig through the "actions" tab from a profile, or I suppose I could try to find it with the LIKE operator in SEDE (if it's old enough). But why not make that easier?
Comments are second-class objects for good reasons and aren't indexed by Google generally searchable on-site, but I don't see the harm in making it a little easier for established users to find them.