Cedric Schmidt

That was a private survival server running pure vanilla.

Of course I cannot be sure that this also works without Optifine, it would have to be tested out. I myself can't really do that because of the 30-day period in which you cannot change your name. I just did discover some interesting behavious: This bug keeps occurring whenever I relog onto the server. Even did this without Optifine, and it keeps happening ... interesting enough? Also tried it on another server, where I spawned where I logged off a few days ago. Have played on there, since.

I doubt that Optifine has anything to do with this. It does not modify the game itself, or the connection to a server.

I do not see how this is a duplicate of the linked report.