Rating loss

I played a rated game with someone rated about 100 points more than me and lost 81 points. How does that happen?

Because you had only played one rated blitz games in the last four years. There is a component of ratings that looks at how often you have played and it judges whether your rating is accurate or not.

If your ratings fall into the area where they are considered as possibly inaccurate, ratings adjustments can be large until the uncertainty falls. I see that you won a game in June. Your blitz rating rose by 84 points after that game.

https://support.chess.com/article/210-how-do-ratings-work-on-chess-com

Thank you Justbefair for your reply to my inquiry. I understand your comments, and I read Erik's further explanation offered in the link you embedded. Erik offered a valuable link to Dr. Glickman's original paper on the Glicko system which was terrific. After digesting, as best as possible, the ideas of this rating system, I wish to respectfully suggest that Chess.com publish each members "Rating Deviation" (RD) adjacent to their "rating". For example Blitz 1600 RD=350. The data is already available and folded into the Glicko rating algorithm used by Chess.com. Staying more aware of our own RD, and that of potential opponents, could provide useful information as we decide with whom to play rated games.

That used to be available on the website but was removed. I think it was likely because most people didn't understand what it meant.

You can view the value through the Stats API

https://www.chess.com/developers

no

Thank you Martin and Justbefair for your helpful and informative replies. Your tireless work helps keep chess.com the terrific community that it is. I can certainly understand that the folks coordinating the site have the clearest view of features, such as posted RDs that are useful and extraneous. I am thoroughly enjoying being a member here, and that's largely due to the hard work of folks like yourselves! Cheers.