Since our little IRN's insanely favorite food happens to be bell peppers, thought I'd weigh in!
Bell pepper seeds aren't toxic (at least according to the stretchy searches I did on them) - however to us humans they taste slightly bitter and not that nice. Birds however, love them.
Having said that ours just loves bell peppers and peppers in general. The fleshy part and the seeds both! He's completely nuts for them. His favorite in particular are the yellow ones. If he happens to be in his cage and he sees us handle one he goes totally nuts and gets super excited.

Go figure, I myself don't care for them too much. I find that if I have some the after taste lingers for ages!