When trying to use the Abusefilter variable article_first_contributor in eswiki filters, I found that the only way for the condition to return true is: article_first_contributor == "". I don't know if the variable works in other wikis, if other variables are affected, or if it has worked before, since it was implemented ( T69793).
See AbuseFilterVariableHolder.php for the relevant code.
- The article_first_contributor AbuseFilter condition should function properly on all wikis with AbuseFilter enabled
Note: this may be a bug on all wikis; this ticket includes checking out whether the bug applies everywhere.