|Open||Jrbranaa||T204747 UserMerge: Code Stewardship Review|
|Open||None||T106123 Extensions needing to be removed from Wikimedia wikis|
|Open||None||T216089 Undeploy UserMerge Extension from WMF production|
|Open||None||T218160 Figure a way to keep usermerge log entries|
The canonical way to do this is to write a UserMergeLogEntries extension that does nothing but define the log type and the associated system messages exactly the same way the UserMerge extension does it.
Another solution might by to just declare the log type by adding something to $wgLogTypes in the config, and adding the necessary system messages to wikimedia-messages. This might be sufficient, but I have not investigated.