The obvious problem is that no two people have the line situated in exactly the same place, which makes for some interesting disagreements. So for instance when I was listening to Midweek on Radio 4 this morning and Libby Purves started complaining about people saying "it looks like X will happen" instead of "it looks as if X will happen" I had a moment of scoffing at her clearly ridiculous pedantry, just because that happens to be a usage I don't care about, or, probably more significantly, don't bother to observe in my own writing or speech.
The context of the conversation was that one of the guests on Midweek was Rebecca Gowers, the great-granddaughter of Sir Ernest Gowers, author of the still-in-print usage guide Plain Words, which she's just edited a revised and updated edition of. (You'll note that ending a sentence with a preposition is a grammar law about which I am not especially bothered about.) As far as I can gather the original purpose of the book was to encourage the cutting away of unnecessary frills and jargon from written communications - presumably of the "I remain, sir, your lordship's most humble and obedient servant" variety originally, but still relevant in these days of thinking outside the box and leveraging our core values going forward.
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On the other hand, Spiked's Brendan O'Neill (writing for the Telegraph) reckons it's all OK and we should stop worrying about it, and, moreover, pointing out that the astonishing invective directed at women on the internet might just possibly be a window on some underlying societal problems is pretty much literally equivalent to implementing Nineteen-Eighty-Four-style totalitarianism. On the other hand, Brendan O'Neill is a tiresome professional contrarian and an utter bellend. You can fill up your Male Privilege Bingo card here: "the standard of discussion on the internet leaves a lot to be desired", "incivility", "delicate sensibilities".
Back to the pedantry: it's also true that a nit-picky obsession with the minutiae of spelling and punctuation at the expense of engaging with the content of the writing is a bit irritating, and suggests spare energies that might be more productively directed elsewhere. If you're involved in a heated online discussion about, say, the conflict in Syria, and you're derailing the discussion by taking issue with someone's usage of the word "decimate", you're probably not contributing anything useful. Barracobarnergate in particular illustrates how fraught with danger taking someone to task for spelling and grammar mistakes on the internet is, given that Muphry's Law will always apply.
On the other hand, writing and language exists to convey meaning and some agreement on what means what is crucial. Take “infer” and “imply” as an example: we need to have agreed meanings for words or communication will be impossible. That particular example might be resolvable a) because it’s not that important and b) by reading for context, but if I start saying “banana” when I mean “horse” and then getting all uppity and DON’T YOU OPPRESS ME when people have no idea what I’m talking about, I don’t think anyone would claim it’s somehow everyone else’s fault.
On the other hand, words' meanings do change over time, and eventually the "wrong" definition becomes the "right", or at least "usual", one. "Disinterested" is a classic example where the switch is probably now unavoidable, by contrast I had literally no idea that there was any other usage for the word "nonplussed" than its standard one of "confused" until I heard my wife use it twice in fairly quick succession in a context where she couldn't possibly have meant "confused". It was only on reading this that I discovered that it's now quite widely used to mean "unfazed" or "nonchalant", which is the context she used it in. You live and learn.
As I've said elsewhere, I try (not always successfully) to be relaxed about this sort of thing as long as the meaning is clear. So I'm not at all bothered about insisting on "different from" in preference to "different to" or "different than", since that's an entirely arbitrary rule that gains you nothing in terms of clarity. On the other hand I'm not at all happy about the "nonplussed" thing, and you can rest assured I'll be having a word next time. In general these days I take the approach of not publicly correcting stuff any more as long as the meaning is clear, while still silently judging people for their crass mistakes.
The other thing to be said about the Grace Dent article is that there's a strong element of: well, you may scoff at her rudimentary language skills and flimsy grasp of geopolitics, but she's got a job and probably earns more than you, you internet pedants with your degrees and your Nobel prizes. What are they worth now, eh? The problem with that is firstly that it seems dubious to judge the worth of a job on the basis of what you can get paid for doing it - by that rationale we value Premiership footballers more than nurses by a factor of several thousand, which I don't think many people would be comfortable with. So while it may very well be possible to make a better living as an eyebrow-plucker and fanny-waxer than as a Classics graduate I'm not sure that equates to a judgment of the two things' respective value. The other thing is that there's an uncomfortable tension between expressing dismay at the internet abuse heaped on women on the one hand, and on the other hand celebrating an occupation that in large part only exists because of some fairly ridiculous societal norms about how women should present themselves to the world: entirely hairless and orange seemingly being the current preference.