Full disclosure, I work at Google, and I actually find positive comments mostly rare, but code review culture is very different team to team, so I can hardly speak for the entire company.

Personally I try to make them often, but I also try to be thoughtful about making them as to not come off patronizing like you mentioned.

Though I’ve never felt like a positive comment ever made me feel patronized in any situation, I think a good way to not come off patronizing is to to make the comment more personal than general, ie:

“This is a cool way to use the rest operator (or whatever thing), Ima steal this”.

Obviously it needs to be an authentic comment, but I think it’s a significant difference vs

“Great use of the rest operator!”

When the interpretation on the other end might be “oh so this person is surprised I know these basic language constructs”.

I learn things from doing code reviews all the time, and I like letting my coworkers know that I feel like I’ve gotten better at my job as a result of reviewing their contributions.

I think it’d be a shame if I didn’t let them know.

> it can come across as patronising

Sometimes, it is worth the risk of sounding patronising.