I can use my Horde mount after faction changing. Is this working as intended?

Don't get me wrong. I'm glad I was able to keep my Great Grey Kodo, but it seems weird that I am able to use it as an Alliance character.

Is this is a bug or are we really able to keep mounts of the opposing faction after the faction change?

Oh yeah, for some reason I'm still in my Horde guild as well. Although it shows that I'm not in a guild, I can still see guild members posting in guild chat.

as far as i know mounts are account wide so u can use almost any mount (except the dk mounts or warlock mounts and so on) so as soon as u meet the requirements u can use it :)

It's a bug. All faction specific mounts are supposed to be changed to opposite factions mounts when changing faction. It works for most mounts but a few are skipped.