...honestly I feel like if you have broken both the bed and the mattress together and you're still at the phase where you're worried about being rude over furniture, the relationship maybe has deeper problems...it always seems like all non-dtmfa relationship letters come down to "be willing to have the hard conversation".

Yeah there's a common thread in a lot of them of, whatever the reason is that you're choosing to put this on the internet/in a newspaper rather than talk about it with someone who you supposedly have intimacy with, that thing is maybe the underlying problem?

And in this case, is that:
-that the LW has been taught that fatness is a shameful thing and you shouldn't mention it?
-that the LW has some beliefs about fatness that make them place a disproportionate responsibility on their partner's size for breaking their furniture?
-that the LW is picking up on shame their partner has about their size/past bad experiences with being shamed for their size, and doesn't know how to talk about that directly?
-generic lack of communication skills/tolerance for uncomfortable conversations?
-etc.?