fascinating
Explanation
The Joke
A cyborg-like character from a future era is complimenting a medieval or Renaissance-era writer, praising the "detail" in their writing -- specifically that the main character uses a "tooth brush" every single day. The humor comes from the fact that this mundane, utterly boring detail of daily hygiene is treated as exotic and fascinating worldbuilding by a reader from a distant time period.
The caption at the bottom drives the point home: "No matter when you live, someone, someday, will write a book about how awful and fascinating it would be to live in your time period." This observes that every era's ordinary life becomes the subject of future historical fascination. The things we take for granted -- toothbrushes, daily routines -- will one day seem as quaint and remarkable to future people as chamber pots and bloodletting seem to us.
The Humor
The comic plays on the way historical fiction romanticizes and exoticizes the mundane details of past eras. We do this constantly with period pieces -- marveling at how people in the 1800s bathed once a week or how medieval people ate with their hands. Weinersmith flips the lens to show that our own boring daily rituals will be equally "fascinating" material for future writers. The juxtaposition of a cybernetically-enhanced future reader gushing over a toothbrush perfectly captures how absurd this pattern looks from the outside.