If the only criteria for allowing posts like these is "People can wish each other well without coming close to that" then HN can easily be flooded with junk posts from every single Religious (and any other) group (Real/Imaginary and Bonkers) for every single day of the year.
If people start posting too many of them, we'll downweight them the same way we would any other repetitive pattern—not because we have any problem with their particular topic but because repetition quickly becomes tedious. (And users would flag them increasingly heavily in any case.)