@SlackHQ you guys need to do a better job with the over write function. Who actually uses this for what? Why can't it be easily turned off? SO ANNOYING.
-
thanks, a combination of restarting, Ctrl R and insert seems to have fixed it!
We're sorry for the trouble with overwrite mode. Are you using a Windows keyboard? If so, does pressing the Insert key allow you to turn it off? How about refreshing the app (Ctrl + R)?
Phewwwwww, we're glad. 
Please let us know if you have any further trouble.