While these situations could be a pg-style astroturf submarine, or they could be satisfied customers (the best kind of advertising), I wouldn't necessarily say fishy (you can look at the satisfied users' previous contributions to make that judgment yourself! :)).
Personally, I've not used Kagi, but I hear positive things from people I trust that use it. So I'll likely try it in the future.
Also, none of these accounts saying nice things appear to be bots or kagi-focused in any way, so I think it's safe to assume they do actually just like it.
Kagi has a free trial, but you have to pay, which is the difference between it and early Google.
Of course, now we have Google ads instead, so who knows, maybe not bots.
I am definitely not a bot.
I am however extremely fed up with Google. And equally thankful that I have found something that works as well as old Google (or better).
The alternative is Searx and I may try it sometimes, but so far Kagi is cheap and very efficient for me (C++ coding and other languages).