My comment about Sinn Fein deciding to take their seats in Parliament was largely tongue in cheek, but not entirely. I do not underestimate for a moment how difficult this would be for them, and some of their supporters would see it as a monstrous betrayal, but it important to remember their goal is to have a united Ireland separate from the rest of the UK, and to do this by political means.

Any hard border within Ireland puts that goal back decades or more, whereas a border in the sea makes unification far more likely. Which the government as a whole would prefer is uncertain, but the position of the DUP is clear enough. So it is very much in line with Sinn Fein's long term goal to stop DUP having the decisive votes on this matter.

I don't think it likely to happen, because the difficulties are so huge, but it looks like it could be another case of a party sacrificing its long term goals to avoid a short term cost.