I'm amazed by programmers who welcome the discovery of a misplaced semicolon but who object to the report of an egregious grammatical error, especially given the fact that both traits affect their employability.
This is a comment thread. The language is informal, spontaneous, largely unedited, and participants come from a variety of language backgrounds. There are going to be grammar differences and mistakes.
You clearly understood the author, as did I and probably everyone else who read the comment. The objection was superfluous. When the commenter took offense and argued, the polite thing would have been to back down gracefully, since the point is entirely unrelated to the greater discussion. Picking on the missed-word typo is just a childish dig.
I don't think that outweighs the evidence from Language Log clearly showing that "which" has been commonly used interchangeably with "that" in good English for centuries. This was linked earlier in the thread. Personally, I'm going to go with Dickens and Melville and Orwell (and statistical evidence) over a blog I've never heard of.
There is, of course, a difference between occasional errors and the way in which millions of competent English speakers use their language, but I'm sure you're aware of the distinction.
I just think it's funny that programmers, acutely aware of the consequences of small code syntax errors, seem peculiarly indifferent to much more significant errors in their English prose.
And yes, I'm aware that many "errors" can be defended as conscious choices. But most of them are neither intentional nor contribute to effective communication.
The English prose used in comment threads like this is written natural language. Programming languages are formal languages. Different treatment should not be surprising.