The trouble is, forget, that grammatically in English, "you" is always treated as the plural form. Hence "You were" is correct - "You was", whilst acceptable as part of a regional dialect (it occurs not only in Cockney) vernacular, is not correct.
The singular form, thou/thee/thy, which also had echoes of the French familiarity of tu/toi/ton, fell into disuse partly for reasons of that familiarity in early Victorian times. Only still accepted as part of
traditional religious worship, the 2nd. person singular is now, curiously enough, considered the
formal version.
The disuse of that from is, IMHO, a pity. It provided a certain amount of subtlety that other languages (e.g. Dutch, French and others) still retain.
As far as the pedantry of correcting others' spelling and grammar, I have not done so yet. I have felt like doing so many times, though. When the author is obviously not a native English speaker, to do so can cause unnecessary upset, hence my reluctance. Were I (that's the subjunctive) to do so, it would be difficult to know where to stop!
Oh dear... my former classics teachers would be proud if they knew how much had, contrary to all appearances, sunk in... One doesn't receive a classical education, one suffers from it!
