mine is two months old, I noticed the yellow mark just after I got it but did not worry about it, then I did a search and yes seems a problem, did a support "online" request, came back to replace it, I called support as I have a the microsoft screen protector
on, they said they would replace that as well. New machine on route to me within 12 hours. Can not complain about the service, just hope it is a new one and not a refurb but may not be able to tell no doubt.
Update, I contacted Microsoft service online, filled in the form and described the problem, within seconds it said send the unit back and replacement would be issued- then message saying new machine had left Germany to me, it was here within 48 hours of
me raising the problem- very good service.
The only problem I now have is the day after reporting the problem my machine had some updates and the yellow line has gone!- Gone completely, vanished.
So I will return the new Surface ( have not even opened the box) and hope the yellow line never returns.
I will say Microsoft - thanks for great service.