Something along the lines of:
[@User] reacted 👏 to your comment [comment...] on [thread...]
[@User] (💖 ) and [n] others reacted to your comment [comment...] on [thread...]
The first one is a bit more natural-flowing than the second, which is necessarily more clunky to avoid giving misinformation (people's reactions may have been different).
I am not suggesting removing the hyperlink to the reacted comment -- you may not remember which it was from the text snippet -- but on a busy thread, where there are comments, sub-threads, replies and reactions galore, it would be quicker if you don't have to click on every notification.