But where it falls down ime is when people would like help in getting through a rough patch, or dealing with the fallout from one argument etc
I've definitely seen threads where people have got decent support for problems like that - perspective from people who have the same annoying failings, support, useful suggestions, humour etc.
But certainly, that type of thread can play to the board's blind spots, which include a tendency to look for abuse in seemingly innocuous situations. That tendency is also a strength, because women here do spot abuse that isn't obvious to the untrained eye.
I suppose most regulars to MN understand that - Chat and AIBU are full of threads about day to day struggles in happy partnerships. That's partly because of different posters saying different things, but you also see the Relationships "big guns" operating within those expectations.
I think the reasonably recent "have this moved to Relationships" advice pints to a shared understanding that the Relationshios board is for serious issues and not petty squabbles.
The problem with that is that newbies won't understand that, won't be familiar with the posters, the culture, the language used, and could end up getting a LTB depending on when they posted and who was around.
The first few posts can really set the tone for a thread, and that can go badly wrong. (As evidenced above when a PP was told she was overreacting when she had been raped by her husband.)
But overall I think the strengths far outweigh those weaknesses.
For something that is just a collection of people posting to help others (mostly women) who are often extreme unhappy and sometimes in dangerous situations, I think it's remarkable.