"K" is usually a short form of "okay", which is either an affirmative response to a yes/no question, or an acknowledgment of receiving an informmational message, depending on context. In most cases, this is a useful response.

Asking a question and getting "I like your question" as the sole response is incredibly obnoxious.

Are you seriously telling me you’re interpreting a thumb up emoji as a literal I like X, instead of applying a little common sense and infer that they probably meant to say „okay“ with that?

I suppose I'd interpret an thumbs-up emoji as "okay" if that were what I saw, but when the server is translating that into an email response that says someone liked my last email, that muddles things up quite a bit.