For keyboarding « and » in vim, I've added four maps:

imap <expr> << "\uAB"
imap <expr> >> "\uBB"
imap <expr> <F5> "\uAB"
imap <expr> <F6> "\uBB"
[download]

I suspect I'll like the first pair of maps more. F-keys are just so far away.

For the rest, hopefully, daxim is right and malformed text is coming to me from the web.

Be well,
rir