I wouldn't necessarily call them fishy, but I am very tired of them. They have a very evangelizing tone. But I think they're ultimately just people excited about the tool they're using and wanting to share it with others.
I took a screenshot years ago where 10/14 of the viewable top headlines on my screen where positive Google discussion. From an advertising perspective it was all earned marketing (satisfied customers speaking highly).
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.
Did we not all evangelize Google in it's early days?
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.
I never say it but here it is: for the price of 2 packs of cookies, I went from being a 1x programmer to a 1.5x programmer without doing anything. If the results are good, it’s good for me and my job which brings me way more money and satisfaction than $10.
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).
Google Search being a bit rubbish has been in the zeitgeist for a while, it's not surprising that people then talk about an alternative they've found that is much better in their experience