I agree that it's confusing. Unless both people are consistently logging in at the same time and only using the pronoun "we" then it's effectively two people using one identity.
I'm quite sure the couples who do this do not share driver's licenses, social insurance numbers, or passports. Their pay cheques are not made out to "Mr. and Mrs. Johnson"
If they're logging in one at a time, and posting at some times as one person and other times as the other person, they really ought to get their own accounts.
If they have their own reasons for using the same account, then as a courtesy to the rest of us, it would be useful to prefix their posts with "John speaking" or "Jane speaking" to avoid the confusion without losing their convenience.
“As I am sure any cat owner will be able to tell you,
someone else putting you in a box is entirely different
from getting into a box yourself.” —bisexualbaker