This plugin introduces new tag and shortcode that turns any text between the tags upside down. This is achieved using unicode characters.
No, all formatting text will be lost. You can use formatting outside, in which case your flipped text will appear with formatting applied to it.
Well, that's a question to browser developers, I think. Unicode character support is bit flakey in some of them, and not all characters are rendered properly. It also seems to be position and neighbouring characters related too. So far I've noticed issues with letter 'p', so just try to rephrase your sentences and experiment to get the best result.