Yes, you can like your own post. By default the Likes extension doesn’t have ranks or levels and so it's not a big deal. And it’s probably the way it is because not everyone wants a forum with gamification/ranks/levels/badges.
I don’t remember if you can vote for yourself or not with the gamification extension. But, that’s probably the extension you want instead of the default Likes extension.
If you installed beta 16, the gamification extension is not ready for deployment at this time.
