Well said by Brian & Brian (from another Brian).
I know of several people who are very bad at spelling and/or grammer & have either sucessfull business's or excel in their chosen proffession & are well respected.
On the other side I know & have met some people who may have been well educated & have perfect spelling & grammer who, because of their total lack of common sense are about as useful as a chocolate teapot. (A bit like many politicians & High Court Judges).
As long as the writer has made a reasonable effort to the best of their ability, then that IMHO is all that matters.
I, for one try to get it close, however, sometimes I "hop on" to the forum just before going to work & "dash off" a reply only to find later about the mistakes.
If you really don't like the way someone has written anything, just do what you may do with someone out in the real world - ignore them.
Regarding text speak - a lady that I know sends texts in full "correct grammer" - no abbreviations, full punctuation, capitals & so on. It must take her ages to send - I know it can take a while to read !
Oh well, back to models railways - just off to the workshop to convert a LGB loco to DCC.