I suppose readability could be judged by some combination of speed and comprehension. To me, Edit: on my pc, the indent font renders as courier new. Now I'm viewing on Chrome OS, and it is rendering as Lucida Sans. :( I use Chrome browser on both.
Just a matter of taste. courier new is God's font.
According to the article Reading speed is now known to be mainly a function of cognition speed, which varies considerably from individual to individual and is not related in any straightforward way (and possibly in no way) to typeface design. Reading comprehension is even further removed from type design.
Those were the initial tests for readability, but are now called into question. The article concludes that there is no proof of readability currently.