Farewell and thanks!

Lacking any other clue (such as accent, mannerisms) that the speaker may have different cultural norms, how is one to tell plain, friendly discoursing from a demeaning, brusque or curt tone? Absent the many critical but subtle cues we receive when engaging in live, interpersonal conversation, the written word - particularly the functional and casual way we use it here - is open to broad (mis-)interpretation at almost every turn. I'll close by saying that, like most of you, I've had the odd run-in with what first seemed like a real twat on the net. But in every case, when we took it up personally, off-list, I've never walked away with anything but a satisfied mind and a more thoughtful and dare I say favorable opinion of the person on the other end.