There are some text boxes on a few forums that the keyboard won't stay up on. If I press on an empty space in the type box, the keyboard will pop up for a second then go away...having the same issue with IE10 on my Surface tablet as well on the same forums.
I am having trouble replying to threads. Whenever I click in the text box on my 920, the keyboard pops up but then immediately disappears. Does anyone else have this issue? So far this forum is the only site that this is happening for me.
I had this issue all the time (on this site only for me as well), and switching to IE desktop worked for me as well (using a Lumia 820). It may also help to clear history since this clears history, cache, cookies, etc.
The only problem I have with IE now is that drop down menu functionality is AWFUL at times. Some sites (like this one) work well, while on others, the drop down menus disappear after I've hovered over it. Very annoying "growing pain" with Windows Phone 8.
I too had the keyboard issue when I first got the phone. It has fixed without me doing anything. The pull down menus can still be a problem for me though. I had assumed it was an IE 10 incompatibility issue.