As I said above I'll give a kudo to just about anything. I'm not following tons of people so it's not hard for me to click a button. What I do limit is comments on Strava to extraordinary (for that person) rides.
There aren't too many places around here to ride so I see people doing the same segments over and over again. You get a good idea when someone has done something different. Maybe it's their first ride on a new bike. Maybe they rode a really long distance. Something like riding 100 miles or doing the Leadville 100 or bonking on the Six Gap ride here in Georgia or setting a new personal record of some kind (and not just some Strava segment record).
My best friend from highschool runs 3 miles a day most days and all I give him is a kudos - and I've known him for 30 years! I've only ever commented when he ran a half marathon and a marathon. But a thumbs up? Sure.