I don't understand what I'm even looking at with that mess of an UI...

I assume you're talking about the "ven1i+'s Pylon: 15 - 2m" with the steve head - but that's no actual bossbar, is it?

I'm gonna try to reproduce this in vanilla.
In the meantime, can you tell me what Minecraft version you are on and what mods you have installed?

Turns out this is the server's custom doing, it has nothing to do with the mod I'm sorry ._.

Oh, no problem!

You didn't have to delete the issue, there could always be someone else stumbling upon this.
(I can't fully delete it either, but that's ok.)

Looking at the screenshot in retrospect, the head has a shadow, so it's using of those pixel fonts to render the head in the bossbar (and all the icons everywhere else).