Just noticed the same issue. I corrected "NSA" several times but it always reverted back to "Nsa". It will be interesting to see if when I hit the "Post Quick Reply" it will revert back, even with the quotations.
It came through OK with the quotes on it??
In this case, it is due to the fact that all replies require at least 1 "small" letter.
Not sure why this is though.