WP:RFC/U redirects here. You may be looking for Wikipedia:Sockpuppet investigations (formerly WP:RFCU) or for Wikipedia:Requests for comment/User names (WP:RFC/NAME)
Prior to a discussion at the Village Pump that was closed in December 2014, requests for comment on user conduct (RfC/Us) were used to discuss the problematic behaviour of specific Wikipedia editors, as part of the dispute resolution process. RfC/Us were an informal, non-binding process. According to the discussion's closing statement, many editors found the RfC/U process ineffectual. As a result, it was closed down on 7 December 2014.
Old RfC/Us can be found in Wikipedia:Requests for comment/User conduct/Archive.