1. I'm not bothered about what your advertisers do, when I click close that is exactly what I expect (on any site) for it to open another tab that needs closing would basically stop me visiting the site again if it isn't honouring my requests/actions.
2. The problem is I didn't click on a page, when I clicked on the close tab (not a tabunder command) so that is what I expect. I understand that sites have a revenue stream requirement, but that has to be open and not in this way.
As an Avast User, there is little more I can do other than point out what I already have.