@itonewbie  In fact, filing MFS for just that would likely be disadvantageous, everything else being equal, when other tax effects as well as additional tax prep fees are taken into account.

True, except those of us in the business tend to overlook the 70 million or so people who prepared their own returns for 2019.  (The number is higher than the 57 million for 2018, because of the EIP returns.)  There will be media reports about how you can save $75 or so by filing separately, and those who are OCD about tax preparation will try it.  Many of them may get it right. 

And then there is my client whose AGI was something like $85,200 in the year when the cutoff for higher Medicare premiums was $85,000.  Another $300 above the line for her (and I'm not sure this actually goes to AGI, I am still looking at 2019 returns) would have saved her about $800.  Sometimes, not everything else is equal.