Tenko keeps talking about he feels itchy when he is at home, that itch is gone after his family died. then it started again when people started to ignoring him. then it probably gone and came again when he met those two punks who hit him, but again it gone cause he killed them.
but it came back after he wear these hands. probably its because he remembered his family s death
it became normal and weird again. i think bubble speech was weird when tenko / shigaraki felt itchy. and the reason is probably his trauma. now, his bubble speech is normal so it doesnt mean he got healed but he doesnt feel past s burden cause probably he thinks like “i am exist to destruction, nothing else to do” (it doesnt mean he is free from afo s manipulation, thats a different subject). i think bubble speech is showing the moments that tenko / shigaraki felt “itchy” (stress).
we knew that tenko felt a lot of stress at that house, he couldnt be himself, hero. he was constantly being punished for no reason. sometimes we felt pycsical pain cause of stress we have. adults can simply say “i feel pain/stress” but kids can not describe these kind of things, abstract concepts.
so shortly tenko cant describe his pain. “it itches” is the way he is saying“i am in pain”. (and probably his quirk activates when he feels “pain” or “stress” or something like that. but its also another subject.)