Consider this query for augroup=Image-reviewer. The group Image-reviewer was recently renamed to image-reviewer. If I wanted avoid falsely stating all users would be Image-reviewers, I would either have to consider the warning emitted or query valid user groups in advance.
Given that augroup is a filter, I would rather expect 0 results if the group specified is invalid, not all users.
Consider augroup=Image-reviewer|sysop -- there only sysops are returned, in spite of the invalid Image-reviewer.
The current behavior is:
- valid filter -> users filtered
- invalid filter value -> users not filtered
- partially invalid filter value -> users filtered by valid part
Was this behavior chosen intentionally?