Sounds like a common issue on Hondas! 2007 honda fit: spark plugs..same problem..torque wrench, 15 ft-lb
When re-installing plugs, inspect the threads and sealing surface which contacts the crush washer (I used sewer camera for that) After removal of a tight plug from cylinder #3, I found a crescent shape impression on the sealing surface; if I would reuse the old plug, the combustion leak could result.

 

I dunno if this is a similar issue but I once didn't torque a spark plug enough and my engine started sounding like a BBQ lighter. Like tick tick tick, in time with the firing of the plug. Took out the coils and one plug was so loose, I didn't think my wrench was on it! It was spinning freely. So I retorqued it to about 15ft.lbs and never had a problem since.

 

There is a lot of mis-information on the link you referenced DrJ!

15K recommended changes... the use of anti seize...the torque value... Plus, the discussion is five years old.

Still, your inspection of the irregular sealing washer is valid. Wish you had a picture.

 

I was so upset I did not take picture by my inspection camera
The only value of Justanser is the linked files from factory repair manuals!

 

When I first replaced the plugs on my 2008 Fit I found that they had a dirty pattern on the threads indicating that they had not been tightened sufficiently at Suzuka. I replaced them with Denso long-life plugs torqued to specs and adjusted the valves and immediately picked up 2 MPG.