Language is a means to an end. If my entire audience understands what I am saying, and is not put-off by how I say it, then I did, in fact, get things right.
You need to draw a line somewhere, or you will end up spending your life obsessing over unimportant details of what you write instead of actually communicating.
It may also happen that the one person who you felt was not "worth the trouble" turns out to be someone who will be very important to you one day, like a potential business partner or investor, and who interprets your misuse of language as ignorance.
There's a difference between obsessing over unimportant detail and being thorough, IMHO.
OMG u shuld see wat they do in germanny its so different their!
But at some point you do start to get diminishing returns, so there are practical limits to how worried one should be about pedants.
What I'm railing against is more that there appears to be little interest, in general, even to try to get things right. I see this not just in human language, but in business, software development, publishing, pretty much everywhere.
I'm really tired, so I'm not expressing myself as well as I should, so perhaps I should just wrap this up and get some sleep. An iPad is also not the best UI for writing on HN.
Thanks for your thoughtful and thought-provoking response.