Rabbi Yaakov Emden didn’t accept it. And as I pointed out, many other codifications of the Rema have not been accepted. And the Rema never codified that massive expansion of the definition of kitniyot we’ve seen in the past generations.
I know that there is some debate about how far the issue of kitniyos extends; my point remains that one can’t disregard his own p’sak just to be able to eat in someone else’s home (unless his p’sak allows for that, as pba mentioned earlier).
The example of the dishwasher was, in my opinion, one in which even one who follows a p’sak not to rely on a certain heter might do so because of the halachos of blios. Pba’s example would also be valid; a situation in which one held that meikar hadin something is muttar.
However, in a situation that involves a clear issur according to one’s rov (or a talmid chacham’s own p’sak), there is no room for such a compromise. I naively assumed that kitniyos for an Ashkenazi in a Sefardi home would be an example that everyone could agree to.