Heaven forbid that he reports something that appears to be a bug under the 'Report a Bug' category.
In the patch notes, they recently released some update with the Victory/Defeat banners for both Mac and PC. Assuming everything else in game is looking just fine, I think it's reasonable to submit a bug report - I'm not particularly strong on the tech side, but I don't imagine that the end of game animation would be affected by anything that isn't affecting the visuals in-game already anyways.
I myself have also noticed that it is blurry, but I have a potato computer so I just assumed it was just me but this certainly isn't the only post about it.
Unless you've been playing customs or something, you haven't played since mid-July. I was going to assume you had normal looking victory/defeat animations and your generic solutions for the problem were indicative of the maintenance of your PC allowing you to see them as such, but you haven't even been able to see it for yourself. You don't know if having this visual bug is 'lucky' at all - for all we know the lucky people could be the ones without the bug.