It looks like Rey Mysterio is the only WWE Superstar to comment on Punk's signing so far. He congratulated Punk and wrote the following on Instagram:
"Awesome to see my homie Punk at UFC 181 announcing his new career as a UFC fighter! Congrats & wish him the best... Kick some ASS homie! #ItWasAPleasureBeingInTheRingWithU#LifeChanger#CantWaite2SeeUKickAss"