There is a duplicity in idea list report (accessed by ideas/list) for which I have found explanation and consider it a bug (most probably bug on SQL level (or similar higher layer data querying is happening).
This is in general a problem when you have 1 main entity (maybe happening only when you have 1 main entity + 1 related entity, not sure) and you use filter from an entity not defined in data model for the report.
Data model: ideas, related product
Filters: Product Name, Idea status, Created by Aha! User:Any (from feature request)
Columns: (not showing feature requests related columns)
I understand that from one standpoint this is “as designed”. But I have user complains about this and I believe their perspective should have preference – there are multiple product designs that can be done, could you please do something?