This deprecated sources list is an excellent resource. I couldn’t find a similar one on the Portuguese language site. Are there such lists for non English sources?
Every language edition of Wikipedia has their own rules and processes. The Portuguese version appears to have a place to discuss the sources for specific articles, but no blanket list of deprecated sources: https://pt.wikipedia.org/wiki/Wikip%C3%A9dia:Fontes_confi%C3...
I don't see an 'extended discussion' section for MPN... There's one for "LifeSiteNews" below it though; are you sure that's not what you're referring to?