I'm a 'member' but don't see where to add an avatar. Am I permitted?
No.
I see a gold border (only on the right) on the picture that is on the OP, but this is missing from your avatar. I don't think it is fixed
So basically it was fixed for a while. Both had gold border on the right. Now it's unfixed. No gold border. Spooky

I don't think that its a problem with the avatar, I guess its just happened because I guess Marco har
rechanged the avatar himself and now he has uploaded the image with no border and that's why its looking like that(only Marco could clarify) otherwise its completely absurd to assume that the website has problems with borders are other parts of the image.
@marco, here is the reason why you avatar took some time to change(earlier)- "After you upload your avatar, you may need to reload some pages to see it." , this is mentioned on the avatar upload page and is related to caching issues.