"Ahh but English is a living language..."
That old chestnut, the next to last resort of the philological wanton according to whose bible there are no such things as misspellings, merely variations in spelling.
It's funny that in your hubris you should attempt to correct someone and then try and evade the embarrassment that comes with the discovery that your correction is, in fact, in error, by employing such a plausible device.
As for your link, what's your point? That Brian Taylor got it wrong, too? Many well educated people will speak of a slither to convey the meaning "a splinter" or "a small slice" when it is completely incorrect and people have written complainingly on these forums of chaffing when they meant chafing. That so many may misuse words or wrongly spell them doesn't somehow endow such misuse and misspelling with legitimacy.
Notwithstanding its etymology, shtum is a completely different word from stum and they have totally unconnected meanings.
By the way, blether is a Scottish version of the English blither or blather. You put your faith in the Scottish as paragons of spoken and written English if you must but remember, they can't even accept that "Scotch" is a valid English word to describe them and all things that have their provenance in Scotland.
Edited: 20/08/2011 at 10:50