Ryan,
Here are 2 videos. I am running Windows 7 Pro 64-bit SP1. One video is IE9. The other video is Chrome39.
Curiously, I wasn't able to reproduce the issue with double letters. If I were to switch into HTML mode when it was happening, I doubt it would show duplicate. I think it is just a browser rendering issue.
Are there minimum browser requirements for the current version of Jive we're using now?
Curiously with Chrome, near the end of the video, I was typing letters that weren't appearing. However, after highlighting the area where I was typing, then they would appear.