Takes a few seconds to find it: https://github.com/thunder-app
But if I understand OPs point correctly Thunder doesn’t seem to do that. As a matter of fact, at least by default, it doesent even compact the same posts.
And yeah, missing out on being able to see comments from multiple threads (hopefully with a noticibly marked community context, so its not lost) is really missing out on the possibilities given by fedi.
The what now?
…
FFS… The skate park was thriving. Then a right-wing YouTuber bought it.