DIASTEMA? That's a … gap in one's teeth? I was confused at the end of my solve, having missed the concept, but I got a nice a-ha when ...
read moreDIASTEMA? That's a … gap in one's teeth? I was confused at the end of my solve, having missed the concept, but I got a nice a-ha when I realized that John split theme answers so that they were "gap-toothed": TOOT / HIS OWN HORN, DO UNTO / OTHERS, SPREAD TOO / THIN. Fun twist on the old "words hidden within theme phrases" theme type.

DIASTEMA is an unusual revealer. I might have chosen to go with GAP TOOTHED so as to be more transparent, but there's something to be said about using DIASTEMA to delay the a-ha moment; to make the solver work for it. It does run the risk of the solver finishing the grid without understanding the theme, and putting the puzzle aside.
I get John's point about matching verb tenses in the themers, but I found the lack of symmetry odd. Along with DIASTEMA being in an unusual location for a revealer — with no symmetrical theme answer — the layout felt a little clunky. Other solvers might not notice any of this, but symmetry is such a core feature of crosswords that breaking it requires an extraordinary or theme-specific reason to do so, in my book.
I wonder if it would have helped to split MOLAR, CANINE, INCISOR, etc. instead of just TOOTH? Or to use TEETH?
Some tough fill. Totally fine to use esoteric words in a Thursday puzzle, like DUMONT, RYDELL, NESSUS (and DIASTEMA!). But too many of them can be a turn-off, especially when they leave room for a solver to finish with an unfair error. I finished with SHIEST / RIDELL instead of SHYEST / RYDELL, and DOMONT / CENSORED instead of DUMONT / CENSURED. Ultimately, I think both errors are more on me than on the puzzle — SHIEST is apparently a variant spelling — but that didn't stop me from coming away frustrated.
Neat concept, fun to see those gaps in the TOOTHs (maybe it should have been TEETH!). Some problems in execution, though.