Can you change the font size in MC's options (under View)?
Yes. Tools > Options > Tree & View > Advanced > Select font .
Unfortunately this causes MC to pick a new font. I believe it's Lucidia Grande. This font looks quite different than the default font. I've never been able to figure out the default, as it's not listed anywhere (in the INI files) and doesn't show up in the font picker interface when trying to change fonts or sizes.
So if you change the font size, it's effectively a one way trip: You can never get back to the original font without manipulating the User Settings.ini file. Luckily I already knew this and I made a backup of the file before I made a change today as a test. I was hoping that maybe this was working differently now, since you asked about it. Unfortunately this functionality is still not exactly what you would expect, and for me, it's not a great solution. It's pretty weird behavior really.
The good news is, I'm very used to the way that MC looks, with the default font, at 100% size settings, on my current system. So I'm happy.
But someone might want to look into the font issue I've described above.
Brian.