Alright, I will replace the dash with a red bikeshed when I get a minute. 
My goal here was to call out that Windows is not recommended for new users despite being a Tier 1 operating system. A dash was the smallest edit I could come up with that wouldn’t break things. I figured a key was sufficient, but apparently everyone has strong opinions about symbology.
If you think this chart is bad please take a look at REP-2000 which is where we usually send people with questions about operating system support. Quite frankly, I think we need to overhaul the Tier system entirely. I am getting pretty tired of angry new users complaining when they try to install Jazzy on their Mac and it doesn’t work.