They are supposed to be funny, but the salty ones also serve as a humorous sort of passive-aggressive way to let go of bad vibes. With the knockback EXP, you can exercise a moment of power over someone's post while simultaneously giving them a gift, sort of like a "no hard feelings". I imagine some instances where people would start an argument over something stupid will be Quelled by a Spell (copyright pending)
Of course some people will have a blast getting in spell wars back and forth between two users. Just a different playing style.
I mean this is how it works ideally, in practice there will be people who get

over spells, which is why we've included the option to disable both casting and receiving them.
But disdain is a natural part of being in a community, and usually people are just punished for it. I think it's an interesting idea to be able to express your misgivings in a controlled way without starting an argument.