Issue Summary

User mention popup window does not appear when using large text in Text Editor mode. This issue can be reproduced only in the Google Chrome browser and can't be reproduced in Firefox. In Visual mode, the user mention popup works as expected.

This is reproducible on Data Center: (yes)

Steps to Reproduce

1. Create a new issue
2. Add a new comment and switch to Text mode
3. Insert a text from the attachment big_comment_example.txt
4. Try to mention any user adding @ - User Mention popup will not appear
5. Delete some text or reduce comment size and a User Mention popup will appear

Expected Results

The user mention popup window should appear when using large text in Text Editor mode in all the browsers.

Actual Results

The user mentions popup window does not appear when using large text in Text Editor mode in the Google Chrome browser. Attached is the screen recording where first I tested in Google Chrome and the second test was performed on Firefox.
UserMentions.mp4

Workaround

In this scenario, the Firefox browser can be used to mention users with large text in Text Editor mode.