Someone who is involved with the happenings of the YouTube commentary community to an extreme, almost obnoxious degree. They spend a lot of time ranting ("Sperging out") about petty drama and have extensive, often unnecessary knowledge about said dramas.

Said people often have no life outside of the internet and spend their spare time in commentary discord servers or calling into livestreams to "Debate" others on recent drama, Despite Usually having no following of their own. Often, commentary spergs are used by the YouTubers themselves for information about events in the community.
Person one: I just found out that in a 2018 livestream, *Youtuber* made a negative comment about Keemstar-

Person two: You're such a commentary sperg.
by metaz January 19, 2023
Get the Commentary Sperg mug.