I was in a world on Xbox one (recently updates to 1.2.9) and when I send to chat I made a mistake. I went to do a backspace and it wouldn't work. I tried it on a keyboard and it didn't work.
Steps to reproduce:
- Place a sign.
- Type words rapidly enough to invoke the lag described in MCPE-28255.
- While the lagging text is being displayed, press the Backspace key.
- Observe that pressing the Backspace key no longer has any effect.
The problem doesn't happen every time, so you might have to repeat this procedure a few times.
Also see comments below about persistence within and across worlds.