Created attachment 433430 [details] Example of a selected border When double clicking next to an element with a border it will select the border (noticed on githubs issue list) To replicate visit an issue list on github (https://github.com/doctrine/DoctrinePHPCRBundle/issues for example) Move your mouse to the right of an issue row, near the bottom of it and then double click and it will select the lower border.
I can confirm this as well.
<rdar://problem/80848914>
It appears that we're selecting whitespace here which is producing (I think) a zero-size box.