I don’t use my personal account, all my money is in my joint account. I switched back to the sole account and happened to notice that there are monthly report notifications which I don’t get on the joint account. Of course for personal account this isn’t useful as its always 0 but it would be nice and useful to have the notifications on the joint account too.
Unfortunately, there’s quite a few features that only work on the personal account. IFTTT being another big one.
Monzo doesn’t appear to be particularly interested in account parity. The Joint Account was pushed out as a ‘me too’ and hasn’t seen much attention since.