I suppose if I had grown up on IRC/MSN/AIM/whatever or had/have a mobile phone it may be different but I have a far harder time trying to decipher a mess of letters, numbers, "acronyms" and SMS terms than any language I have ever learnt. There was also a study done a while back where the first and last letter was found to be all that was really needed for some people, it would seem however I am not one of those people which I would speculate is half my problem.
I spend a fair bit of time reading foreign languages sites as well, granted I may not be brilliant at the various languages contained within but text/leet/donkey speak "native" to said language often throws me completely. I can not speak for others here but I am fairly certain the same applies in reverse and looking at all the various flags sported around here....
Oh yeah, strictly speaking the contractions (don't, can't, you're.....) should be a thing of speech and quotations thereof. They should not appear in written text.
As for me pulling someone up I tend to either ignore something with atrocious use of language or decipher it and then rewrite it in ye olde/very formal English. Personally I try and write on forums like I would write an SMS message, which is like I would write an email, which is like I would write a formal letter.
I would like to believe I pull off a level of readability most of the time but my tendency to use obscure words when I can not remember the spelling of the more common synonym probably kills any chances of that.
Oh yeah: bar some stuff like sign/sing house/hose unite/untie... the widespread use of browser spelling plugins has made life much nicer.
Next debate: imperial units and the missing "u".
edit: a guide to punctuation:
http://www.informatics.sussex.ac.uk/depart...ion/node00.html