Mentioned usernames are deleted when adding two newlines to a comment

Issue Summary

Some of the mentioned usernames are deleted when adding two new lines when replying to a comment.

Steps to Reproduce

Preconditions: Have a board with four members (A, B, C, D)

Steps

1. @ mention the other three users in a comment on a card with user A
2. Switch to user B
3. Open the same card, and click Reply just below the comment
4. Click on the first or second @ mentioned user name
5. Place your cursor after the first @ mentioned user, but before the remaining two @ mentioned users
6. Press return twice two add two new lines
7. Type a short message ("hi" for example)
8. Save the reply

Expected Results

All @ mentioned users remain in the reply

Actual Results

All @ mentioned usernames after the two newlines are deleted from the reply

Workaround

Press return only once in the description to create just one new line instead of two≥ The issue only occurs if you press return twice to create two new lines in the description.