I had a 2007 Honda Fit. The manual said the same about not recommended and voiding warranty. However, I purchased a hitch for it. I purchased a 4 x 8 trailer from Harbor Freight. I
moved my 1800 sq ft house 30 miles away, to my new one, with the Fit and trailer. Zero issues.
I had a trailer hitch on a CRX that I owned. I moved 180 miles away with it and a small U-Haul trailer.
I had a hitch on a 1999 CR-V. I towed the above-mentioned CRX from western Kentucky to Washington D.C. and back.
I have a hitch on my 2006 Acura TSX. I used it with the HF trailer to move from TN to NC (500 miles one-way) and back over the course of a year. Again, zero issues.
Since I have the TSX, a 2014 Pilot, and we have a GMC 2500 pickup, I don't have a need for a hitch on the Clarity; however, I wouldn't hesitate to put one on it if that was what I wanted/needed.
If you research, you'll find that there are many autos in the US that are not rated to tow anything (Fit, included -- it's call Jazz in Europe) but it is rated to tow in Europe and other parts of the world.
Maybe we just have the most over-protected, lawyer-based place in the modern world?
It's really sad that people have to be told not to do stupid stuff -- like drinking disinfectants, etc. There are warning labels on everything because we've become a society where people do things that are, well, rather stupid. Most Darwin awards are extremely justified. Use some common sense. A small trailer probably won't be an issue. Towing a 3000 pound car on a 2000 pound trailer is probably asking for a Darwin award.
If you want to put a hitch on your Clarity, go for it. eTrailer sells them:
https://www.etrailer.com/hitch-2018_Honda_Clarity.htm wiring adapters, too.
Disclaimer: My opinion does not represent Honda, Acura, or any other affiliates. My opinion is mine, and my own. My experiences are not recommended to others. I do not advise doing anything that would make a lawyer smile and/or drool.