Checked many cases, only the following present some slight problem with highlighting.

1. On a page watched by some user, edit that user's post several times. The user receives a notification which when clicked directs to a topic page with correct highlighting.
2. Edit a different post in the same thread multiple times - does not matter which one. The user who watches the page will not receive a notifications about somebody else' post being edited.
3. The user whose post was edited receives a notification: "Your post was edited multiple times"
4. Click on the notification "Your post was edited multiple times".

A user is directed to the topic page where highlight (a vertical bar) will be applied to all posts for that topic.