Okay, here's an odd one.
When do custom directory for uploaded avatars, it somehow ends up with broken images when upload.
When looked at the image's URL, it shows both the URL & the path.
Upload Directory: /home/name/public_html/avys
Upload URL: https://www.name.tld/avys
When try to see URL for broken just uploaded avatar:
https://www.name.tld/avys//home/name/public_html/avys/avatar_496_1481822533.png?time=1481822533
As can see, there's indeed something odd with that.
This is confirmed on 2 forums.
However....
Here's the kicker. If let it show after save on uploading, as broken, and click Forum Profile again under modify, the avatar then shows correctly. So, this bug is only on initial avatar upload and save.