Created attachment 216166 [details]
HTML example showing the issue with offsetTop property
As you can see in the attached HTML example, offsetTop doesn't return the same value than getBoundingClientRect().top for an inline element in the second region.
If you mark the element like "display:block" the issue disappears.
Created attachment 216170 [details]
Comment on attachment 216170 [details]
Assuming that patches for review since 2013 are stale, r-