Until it is mentioned (often afterwards), how would one know the person is neurodivergent? Is it fine to correct someone making those mistakes who are neurotypical?

I think how the correction is made is the differing factor, because you can never have complete information about the people you reply to on a platform like this.

On the other side, there is definitely a time and place to correct people for simple mistakes, especially if you still understand what they mean. Replying to someone asking for help in a matter is probably not one of those times. Replying to someone pointing out other mistakes or lack of knowledge, I think, is a fine place to make corrections (respectfully).

Especially if no one is called out by name and insults aren't being used.