FWIW, I’ve been tracking this for a few weeks, and the rMSSD has varied from a low of 49 to a high of 186. Weekly average has been around 120 or so.
The HRV4Training app lets you compare your own values to a distribution of a bigger population, filtered by gender and age. This implies it is possible to compare metrics from one person to another. Of course, they also let you compare your HR to that of other people, which strikes me as a dubious proposition.
I’m not sure about how valuable or meaningful any of this is, but it does underscore the point that I do a crappy job getting enough sleep!