I wouldn't blame spell checkers for this one. People had difficulty spelling long before there were spell checkers. To go way back, Spenser (who wrote "Faery Queen") couldn't even spell his own name the same way consistently. I've met a number of people with poor spelling skills who are older, so the atrophy due to spell checkers arguement just doesn't hold up.
I don't agree that spelling and intelligence and/or reading skills necessarily go together. I have met some people with impeccable spellign who I wouldn't rate as geniuses. I have also met plenty of people who are intelligent and have very good reading skills, but are atrocious spellers (I tend to include myself in this category).
While posts should certainly be written well enough to be clearly understood, a few misspelled words should be forgiven as long as the point gets across clearly.

oops, hit the wrong button. This should have been a reply to "lack of language education."

Well, of course this is my field, and as a writer and teacher of writing, I notice every jot and tittle (what is a tittle, by the way?) I, too, want to jump in and say "It's breathe! Not breath!" which I have actually done a time or two. The trouble with such errors where I am concerned is that they stop me in my tracks, break my concentration and sometimes ruin a good post if too frequent. But that's just me. I don't think we need worry about it too much here unless the question is incomprehensible (just ran into one today, as a matter of fact).

Catty (who can spell almost anything, but can't tell whether the breaker is on or off, despite being married to 2 electricians)

Catty, A jot - from the Greek letter ‘iota' = ‘i' - means the least part of any writing. It can be applied to dots, strokes, Spanish tildes etc. A tittle is defined as a small stroke or point in writing. The two words are, therefore, effectively synonymous, even though they are usually now combined in the phrase "not a jot OR tittle".
There is a tendency to suppose that the jot is somehow tied to the 'i', because a dot is what the letter ‘i' has and they share the ‘i' sound via the original word ‘iota'. By the same token, the tittle is often supposed to relate to the stroke on the ‘t', perhaps because they share a ‘t' sound. However, either can be used for the i-dot or the t-stroke, really, or any other such mark.

Spenser wrote 'Faerie Queene', too, or at least his printer did,for the edition of 1596! Surely the only rule of spelling is that it should not confuse or irritate the reader.Some traditional spellings are irritating enough anyway.So 'gaol'for 'jail'has been a long time dying but seems to have done so now. It's a pity that Dr Johnson and other lexicographers did not adopt a more robust approach than they did when they had the chance. The French periodically revise their language and spelling. So 'clef' (key) has lost its F, for example. They of course have an academic body to lay down the rules. I suppose it's too late for English to become like Welsh. Every Welsh -speaking child can spell as soon as it can read. Although strange to English eyes the Welsh language has strict rules of orthography which are simple and consistent.(Only snag? Commonly Welsh words change at the beginning because of the word that precedes them!This makes perfect sense to a Welsh native but drives the rest of us crazy when using a dictionary!)