It's not an age thing, It's the same reason the internet generally got toxic after a time people who aren't passionate about things take over and drown out the high effort contributers
I think there's a difference between typos and the grammar of someone learning the language.
Meaning that you can usually differentiate between a native speaker of your language typing hastily and not bothering to correct themselves of clean up, vs a new person learning your language speaking in a generally broken manner. I think by typos OP was referring to the first case, and was probably not accusing ESL learners for having imperfect grammar.
Don't underestimate me I can do both. May be he did discriminate though.
Better point would be to speak about argument being more constructed and than one sentence on lemmy compared to reddit ?!