I get the impression a lot of people who consistently leave a kudos and no comment are just not interested in comment related conversations: they have social anxiety, they can read English but not write in it very well, they just don't enjoy comments, etc.

I am someone who leaves a mixture of comments and kudos. If I leave a lot of kudos on one author without commenting it's either because I liked the works but don't have anything much to say about them, or I'm not in a commenting headspace due to mental and physical health issues. Either way the author asking me to comment would easily make me very anxious and self conscious and probably just discourage me from leaving kudos on other works.

As a writer myself, I always work on the assumption that writers want comments, and leave them as much as I can. So there's not much an author could say to make me more likely to leave one, even an author whose works I enjoy. Maybe making commenting less of a cognitive load by saying "here are some specific things I'd be curious to get readers thoughts on" etc would make me very slightly more likely to do so but that's about it.