>>15
You are correct that it does have to do with the time span the speaker is picturing in their mind. As for why I (a native English speaker and fluent-but-not-native acquired-Japanese speaker) know the grammar better than you, it's because I had to learn the grammar and then speak it. You learned to speak it and THEN learned the grammar.
So you speak better, but I may know a few grammar points better--likely not, though. I just got lucky this one time. It's a lesson I remember from when I lived in Kanagawa.
But if you're Japanese and not Japanese-American, your English is extremely good--dare I say "flawless"? I didn't detect ANY hint of non-nativity in
>>15 at all. I'm jealous; I wish my Japanese were that good.
Speaking of "were," here's a grammar point from English that is similar. Technically, "I wish my Japanese WERE that good" is correct, not "WAS that good." The reason is that you are supposed to use the subjunctive mood rather than the indicative mood for situations that don't actually exist in the world (e.g., hopes, wishes, desires, some conditionals, etc.). "Was" is the indicative, and "were" is the subjunctive for the first person singular.
However, you will still find a bajillion results for "was" in that usage, because it's "wrong" only in prescriptive, rather than descriptive, grammar.
The only reason I attacked
>>6 prescriptively is because I thought
>>6 was the same person as
>>2, whom I considered an asshole.
And on the subject of out-of-use grammar, don't get me started on who vs. whom!