It used to be the case that Upload Wizard checked titles against the title blacklist ( https://commons.wikimedia.org/wiki/MediaWiki:Titleblacklist ) as you updated them in the "Describe" step. This check appears to have been broken somewhere along the way. We still have a catch-all check once the user presses "submit", but that's a slower and uglier way of doing things.
It'd be good to restore the original check.
(Tested in Chrome 22. Steps to reproduce: Upload a batch of files and give them titles like DSC03435 - expected behavior, warnings should appear immediately. Actual behavior, warnings only appear once files are submitted.)
Version: unspecified
Severity: normal
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=43009