Wow, some really outraged comments so far...

Bottom line: if you're going to work for a company that does significant work with language and documentation, your grammar had better be up to it.

Further, if you're hoping to get into a role where attention to detail really is important, yet you still (after a couple of decades) can't figure out how your own native language works, you're not really suitable for that role - because the implication is that your purported 'attention to detail' isn't truly so.

Is that really so unreasonable??