it plugis or vanilla features what this verion
grep is your friend.
❌ ✊ ♥. ¸. ••. ¸♥¸. ••. ¸♥ ✊ ❌
It's the Reactions addon; it comes with hosted VanillaForums.com plans and is not available in open source.
There are some open source alternatives that vrijvlinder has linked.