To an extent, but mostly in the "top kek/praise kek/kekistani" sense, and the more recent "KEKW"

If it's simply used in place of "lol", that's an old WoW reference - "lol" written by Horde players reads as "kek" to Alliance players, and people have been using it in that way since the game was released

...for what it's worth, calling things "Reddit" when they aren't from Reddit is also a little on the Rule 8 side of things