I think games with taxes is what causes USCIS ask for joint sponsors, ask for more docs and the latest tax return transcripts.
If we all recommend to be transparent and honest with government dealing with immigration, then why do we have this double standard when it comes to taxes? IMHO if married, I'd always recommend filing as MFS or MFJ. If it means inconvenience and paying more to government for that year - so be it. Filing single when married is tax fraud really...