There are a few things that I think it's very important to realise about being excessively pedantic with regards to grammar and adhering to established conventions.
1. The English language is a bit of a mess anyway. A wonderful, complicated and fascinating mess, but a mess nonetheless. It has got to where it is today by the bending and breaking of rules and the cobbling together or words. Whereas some would consider a contraction such as 'gonna' too informal to be acceptable, it does, at least, have a purpose - beyond saving a few precious characters in a text message. It sounds different. It has a different ring about it. This claim cannot be satisfied by contractions such as ‘wuld’ (instead of ‘would’) or ‘u’ (instead of ‘you’). These, to my knowledge, have been created solely to save space in a texted message and, in my opinion, can hardly be excused in a written, or typed format. They do, again in my opinion, look vulgar, and although they may save the odd microsecond here and there, a lot of time could also be saved by saying nothing at all.
2. Style. How many people have been pulled up by Microsoft Word’s grammar checker on a stylistic ‘error’? Sometimes, you
want to say things a little differently. Everyone has a different style of writing and much can be achieved (comedy and poetry are good examples of this) by the deliberate bending and breaking of conventional rules - which, after all, are there for the guidance of wise men and the obedience of fools.
3. Good grammar is important, but so are good manners. Aggressively pulling someone up for not following (and likely, not being aware of) relatively obscure artifacts of the English language reflects more unfavourably on the corrector than on the person being corrected.
Overall, grammar is very important; it’s the guardian of emotion and inflection within the written word. I believe that unchecked erosion of these rules would run parallel with (and be symptomatic of) an erosion of civil society. I’m as annoyed (and frankly, worried) by all the CD’s and book’s your likely too find out their, but politeness costs nothing – and is a more likely vehicle to your viewpoint being listened to than supercilious hostility.
Besides, bad grammar and writing is what keeps me in the job