I absolutely agree with Rosie when she says "what I find most disagreably pompous, is where a posters otherwise *very clear content* is ridiculed or dismissed, because they incorrectly spelled a word or used an apostrophe where it wasn't required."

If the only way you can attack someone is picking holes in their spelling or grammar rather than tackling their genuine and well argued case, it is tantamount to admitting that you have lost the argument. It is unfogivable. It is beneath contempt.

I hardly ever do it.

In the case mentioned by Insane Beard above, the usage I took exception to was "I could of added...". Passing over the true horror of that blunder, the point is that it was made by someone who worships Englishness, albeit a totally fictional Englishness largely of his own invention. If he couldn't even get the bloody language right, 'e 'ad it cumin'.