Something I've noticed while talking with francophones in my town --
English is unusual: it has two levels of grammar. The first is
inconsistent, but relatively easy to learn, and it allows people to
speak with ease, confidence, and clarity. The second level is hidden,
and pops up when we try to write with a similar ease, confidence, and
clarity; we find this harder than we had thought, because the
hidden level of grammar now makes demands on us. The subjunctive mood,
case forms, complexities of tense: we can talk all night and straight
through to dawn without using them, but when we write, we need to
understand their functions.