Meta: irreplaceable bvas

Posts that have a higher quality or resolution version at the source that cannot be uploaded to e621 for any reason.

Common causes
Technical limitations (images over e621's dimension or filesize limit)
The source is no longer accessible
The raw image is impossible to retrieve due to download being disabled or the design of the website blocking downloads
Conditional DNP rules make posting the larger version prohibited

This does not include better version at paywall.