I recently asked my teacher about なら being used in this command sentence, and she said while it was acceptable, it had a different meaning compared to 「帰ったら、窓を閉めなさい！」
While the たら sentence seems to imply closing the window after getting home, the なら sentence implies the reverse: closing the window before going home (from the office, perhaps).
I asked, 「いつも 逆のニュアンス ですか。」 and based on her reply I figured yes, なら always implies the second half of the sentence occurring before the conditional clause. (Perhaps either of us misheard or misinterpreted the other person.)
Looking at some of the answers on this website and some example sentences, I can see that this isn't always the case: なら can be used to mean "If that's what you're talking about..." or similar.
(1) If [you] (are going to) buy a tape recorder, [I] expect [them] to give [you] tapes. (Statement of expected outcome. Here I would interpret the tapes to come with the recorder.)
A: スーパーに行ってくるよ。 I'm going to the supermarket.
B: スーパーに行くのなら、しょうゆを買ってきて。 If you're going to the supermarket, bring back some soy sauce.
Am I analysing the sentences above wrongly? When does なら have the 「逆」nuance? When does it simply mean "If that's what you're talking about..."?