There are a few YouTube videos I have watched an commented on over the years, and there are a couple over the last 3 years or so that I monitor my Original comment, and I have noticed today that several of my comments in that period have been relabeled with a similar, but different tag, plus a random number.
YouTube seems to have switched back to using usernames (aka “handles”) on comments instead of display names. I suspect it’s to help avoid account spoofing.
You can edit your handle like this:
On any YouTube page, click on your avatar in the top right.
Choose “Your Channel”
On the page that appears, click “Customize Channel.”
On the YouTube stupio page that appears, choose “Basic Info”
Scroll down to the “Handle” section and edit it.
Not that your handle must start with @ and cannot contain any spaces or punctuation marks other than . or - or _.