-user: was added as a global argument to core in Dec 2008, and backported to compat in May 2012.
https://mediawiki.org/wiki/Special:Code/pywikipedia/6171
https://mediawiki.org/wiki/Special:Code/pywikipedia/10261

However, -user was in use by several scripts, and used for a conflicting purpose.

clean_sandbox.py : '-user' boolean to enable the bot to operate within userspace. It does work, as -user: and -user are different (global arg parsing ignores '-user' as it doesnt end in a colon). However it will present a major problem for the argparse implementation, and is very confusing. It is also buggy: T87634

-userlist was renamed -user in compat, Feb 2012, and copied to core, December 2012
https://mediawiki.org/wiki/Special:Code/pywikipedia/9899
https://mediawiki.org/wiki/Special:Code/pywikipedia/10768

template.py : '-user:' string argument to process pages by the user - impossible to use this argument, excepting selecting the bot's user account, as the global arg parser requires a password for that username.

Added to compat in Nov 2010, and ported to core in Sep 2011
https://mediawiki.org/wiki/Special:Code/pywikipedia/8698
https://mediawiki.org/wiki/Special:Code/pywikipedia/9545

patrol.py : identical problem as template.py

-user was part of the initial compat script, March 2011. not yet ported to core.
https://mediawiki.org/wiki/Special:Code/pywikipedia/9090