Normal targets show up as a small red square above the compass area.

I randomly starting sniping stuff as I walked, and (at a distance) a glowing ghoul showed up as a larger, red diamond shape instead.

Is that just a +++ enemy notice? I don't think I've noticed it before though.

I was wrong. Its recon scope

you got a recon scope equipped on your rifle?

The recon scope 'tags' enemies and the icon is a red diamond.

Recon scope puts a red Dimond on targets you zoom in on.

Sorry Wilson beat me to it lol

Ah that's it. I don't use power armor, but do have a new recon scope. That's why I was testing some sniping.

Cheers!

If you have the "Show Floating Markers" option enabled in your settings, the diamond will also appear above their heads as well, and be visible through walls and everything else. Good way to keep track of enemies in a fight.