Created attachment 208448 [details] Demo It appears that our code to repaint selection gap is broken in vertical writing mode
<rdar://problem/14699394>
Created attachment 208466 [details] More reduced test case
Chrome Canary 118 and Firefox Nightly 118 (after removing -webkit- prefix) does not get any selection but Safari Technology Preview 177 get selection (blue / grey background), just after 'abc'.