I just dimmed an LED using a fine felt-tip marker pen. I have covered it maybe 80%, and can see if it is red or green which is what I need, but it no longer irritates. It is directly under one corner of my monitor.
It's a Faber-Castell Multimark, if anyone wants to know, but, essentially, one of those pens that writes on almost everything, including glass, plastic and metal.
Interesting tip - thanks! I've used matte black nail polish in the past to cover some bright blinking LEDs on a monoprice HDMI switch. (Who comes up with the idea of a blinking LED to indicate the selected channel?) Of course, matte black won't work on Schiit stuff, but maybe there's matte silver nail polish available. (BTW, the lady at the local beauty supply store looked at me kind of funny when I told her that I was specifically looking for matte black nail polish, so I had to tell her what it was for. Nor sure if that the explanation helped.)