Something's wrong with highlighting text using shift and left arrow key

[⭐ Alex ⭐]

This happens on xenforo.com, I don't know if it affects other forums.

In the text editor while trying to make a post, if I hold shift and tap left arrow key to select, one tap left will select one character. The next tap left will clear the selection.

Selecting in the right wards direction works fine, it's the right direction after all, it's just going left that's borked.

Tested on Chromium and Firefox, both are borked.
Something's wrong with highlighting text using shift and left arrow key

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