When in third person if I hide my UI and try to type in chat the normal keybind for that key takes over and it locks you out of chat, and your camera only moves when you right click and drag it. Also you can not pull out your weapon when this happens.
Yeah this annoying bug has been happening for a very long time.
Only way to get out of it is to switch ui back on, get the chat window to show up, and then press on the part of the chat that says group or zone or whatever method of chat you are using, and then select any of the options that show up in the box. This will allow you to move everything correctly again.
Unfortunately no. The best way is to type your emote and enter it, and then immediately hide ui.
There is also an awesome addon called Idle Animations, where you can customise emotes your character does while not moving. You could select the one you want and just wait for your character to perform it and take the shot that way