What version are you running?
3.0.8
What's the URL of the page containing the problem?
https://reviews.reviewboard.org/r/9502/diff/
What steps will reproduce the problem?

Open Firefox on Android
Go to diffviewer
Click to open an issue
Try to type at least two words
After every "space" the previous word will be removed


What is the expected output? What do you see instead?
Normal input like on Chrome or Desktop-Firefox
What operating system are you using? What browser?
Android 8, Firefox 62.0.2
Please provide any additional information below.