I highly agree with most of the above points, particularly in regard to the following:
- INTJs can use grammar to discount an argument.
- Poor grammar creates mental white noise for us, making it difficult to pull meaning from the garbled message.
I would like to add my point of view as to why we feel the need to point out grammar and spelling mistakes to others.
I'm a very typical INTJ technical writer. I don't always feel social enough to point out mistakes, but when I do, it is for these reasons only: to improve the person's future use of the language and, possibly, influence a general change toward better grammar in the world around me. Poor grammar truly is like nails on a chalkboard for me. I know everyone makes mistakes (I do so often), but I feel like habitual things (forms of lay or homophones for there) can be fixed by simply pointing out to the person that they are, indeed, making a mistake. I don't choose humanitarian causes (I'm hardly altruistic in the traditional ways), but I choose to help others to self-improvement in this way. Besides, they may go on to have children and, having learned the error of their ways, may pass on proper grammar to their offspring, as well. It also helps me by (hopefully) snuffing out the poor grammar around me one encounter at a time (of course, it's a constant battle to maintain balance).
I would also like to say that poor grammar gives me the impression that the author (or occassionally, the speaker) is younger and more immature than they actually are. Subconsciously, this causes me to question their intelligence. In recent years, I've tried to curb this a bit, and I apologize now for the way many will hear arrogance in that comment. It just casts the author/speaker in a negative light, and they are putting themselves at a clear disadvantage from the start.
Finally, correcting grammar is like putting the universe back into order. I'm not sure about other INTJs, but that's very appealing (ordering, filing, organizing).
My biggest annoyance is that it only takes a moment to read over something before declaring it complete. It gives me the impression that the author is lazy, careless, and so are their points.
((I do make allowances for phone/PDA users, for whom tiny screen plus tiny keyboard can equal extra mistakes and more difficulty checking it over.))
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**In point of fact, this last bit is why I replied to an old thread. My phone displayed "similar threads," but the dates were hidden behind user pictures. Seeing them now on a "real" computer, I'm somewhat embarrassed. >.< Sorry.