Most forum editors either just flat don't work or yield very flaky results with IE11 as being delivered with the Win 10 previews. Even your forum editor here doesn't work well with it.
Microsoft claims to be listening to feedback from users for Win 10 (something I have yet to see evidence of), and I've provided feedback via the prescribed channels (Feedback App and frowny face), but I'm going to leave a note here too in the hopes that someone who matters might see it...
If you folks think IE 11's experimental mode is close to release readiness, you are mistaken.
FWIW, IE11 on Win 10 with the experimental mode turned off works passably well.
-Noel
Detailed how-to in my eBooks: | Configure The Windows 7 "To Work" Options |