I don't think this is accurate, based on my having asked both airlines this question within the past few weeks. I have six segments on Vietnam Airways this week. Before purchasing the tickets I asked both DL and Vietnam Airways and was assured you get MQS for each flight. I'm also a segments qualifier, so the six segments are a pretty meaningful chunk of change. My flights are not the very lowest fares, but they are each the lowest tier that earn MQMs. (K, L, Q)

Unfortunately, I'm on a flight right now (first leg to Asia, in fact) and not on the computer with access to the email on which I got the responses, or I'd post them. Bottom line, though, is both airlines indicated that if you take-off and land, it's a segment, regardless of how it counts towards MQM.

I was told for domestic flights, no, but for international flights, yes. My first few flights are domestic, but my last flight is DAD-HAN-BKK, so I'll find out.

This is what both airlines told me. I'll know for sure in the next couple weeks on both questions and will post about lounge access and MQS.