Enagonius is my online persona for years. I even plan to eventually transform it into an actual brand of sorts by producing content under that name. I know I can't claim copyright over it because it's an old mythological epithet, but I think I could eventually guarantee its use in a few platforms under certain circumstances. But I'm not here to banther about legal matters – specially hipothetical ones.

The thing is Enagonius is taken here in DnDBeyond and the acount with its username is inactive since 2019. I'd like to know if accounts are deleted after a while so I could finally remove the underline in my username... Or if if there's a way to file a request for such thing.

Thanks in advance for all the help and clarifications!

I don't think they do that here.

Since you want it to be clear that you're "Enagonius" online, I suggest that you request a display name change to something like "Enagonius_DDB" so that the underscore & remainder is like a signifier of this website.