Poetry allows for creative punctuation and grammar, Lucy. I would never judge a writer by "mistakes" in poetry that were likely placed there on purpose to convey a feeling or thought for which we have no "correct" language or for which punctuation is a hinderance.

But, for other sorts of writing, I expect the use of, at the very least, basic grammar and punctuation rules. Mistakes happen, of course, and often they are typing mistakes, not grammar mistakes. But, with all the available free editing programs, it irritates me when a writer makes the same errors over and over. I have a writer for one of my publications who never gets it's and its correct, and, obviously, doesn't notice or care about my corrections. Countless times I've corrected their and there or have added and removed commas. Commas are tricky. I certainly don't get them right all the time, but a sentence shouldn't end with one!

Writing on a platform like Medium doesn't need to be perfect, but it needs to be correct enough to be understood and read easily. Elementary punctuation and grammar are to be expected.