Comment is too long
The trimmed comment is longer than 4000 characters before banned-word filtering runs.
Why this happens
Hard length check on file/folder/news comment APIs. Paste from long documents or logs often trips this. Post-filter oversize uses Comment too long after word filters instead.
Diagnose and fix
1. Visitor: shorten to ≤4000 characters and post again.
2. Admin: no setting raises this cap today.
3. Confirm they are not hitting a different error (captcha, comments disabled).
4. For spam floods, use moderation / filters rather than raising the limit.