Link dialog not well positioned when on the side of a block

[jasmussen]

Describe the bug

If you link text that is along the left or right side of a text box, the link dialog is cropped.

To Reproduce

Try a small viewport, create link along the left side, observe that the dialog is cropped:

Try the same on mobile, and notice you can't even insert a link:

CC: @noisysocks were you looking at the link positioning stuff? Any ideas on how hard this would be to fix?