Duplicate characters are entered when create comment with Japanese with Safari

Issue Summary

Duplicate characters are entered when create comment with Japanese with Safari.
It doesn't looks to occur in other browsers.

Steps to Reproduce

1. Open a issue with Safari browser
2. Switch to Japanese IME and type "toukyou" in comment

Expected Results

"とうきょう" is entered

Actual Results

"tととうとうkとうkyとうきょとうきょうとうきょう" is entered
画面収録 2020-07-27 9.51.59.mov

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available