Speaking from first hand experience, it is NOT mandatory for the US citizen spouse to attend the interview at Mumbai consulate.
My wife attended the interview by herself back in 2012 and I did not accompany her to the interview.
I think some of us are loosing track of the question. If I understand correctly, this thread was about whether to file single or married (but filing separately) when your spouse is living abroad waiting for the paperwork to get processed by NVC, Embassy/Consulate or USCIS.
On that subject, my personal experience based on consultation with friends (who were in similar situation in the past), TurboTax adviser and my company's account payable team, I was advised to file as Married but filing separately and that's exactly what I did.
Now, based on some of your experiences, a few of us were able to get away with filing single. But is that the correct way to report earnings? No, because filing Married but separate has several differences than filing married. A few to name are - restrictions on contributions towards Roth IRA and inability to deduct certain education credits (especially interest on student loans).
So the next question is whether NVC and the Embassy/Consulate has the jurisdiction to reject you based on the accuracy of your Tax Filing? And unfortunately, I do not have the answer to that. Therefore, I had suggested filing for an adjustment to be on the safe side and avoid future heartburn.
My 2 cents...
Trina & Raja got a reaction from M.F in US citizen spouse at interview
Trina & Raja got a reaction from CarlosAndSveta in Has ANYONE filed single on 2011 tax returns and gone to the interview?