I don't think the Axe does feedback, per se; I think you're hearing harmonic content, of which on some patches, OMFG is it glorious!!! Just instantly fades up an octave... Amazing that a modeler can even do that!
Edit: I've also noticed in some presets you can get natural harmonics in places on a string I've never even heard before. I know they're there (it's just math), but the only time I've ever been able to get, for example, the one around the 3rd fret, I've had to have the gain (on a real amp) set so high it was an unusable tone. Not the case here.