Another neat letter-based idea from Jon, this one using DIVIDED BY to represent BY split across the middle — the capital B forms a pair of capital Ds stacked atop each other, and the capital Y forms a capital V sitting on a capital I. I had seen both tricks individually, but to combine them into one — with such a perfect revealer! — was really cool. WITT (wish I had thought of that).
I also loved the fact that the BY in DIVIDED BY was split like the others. Very neat to have the special split happening right within the theme revealer. Nicely consistent.
I got a little confused during my solve, though. The fact that there were other Bs and Ys floating around the grid made me wonder why I shouldn't be splitting up those letters too. It was even more confusing when there was an extra B right in a theme entry: the first B in BOOBY TRAPS. But, I decided that it was totally fair, since there is a clear logic of "only divide the letters B and Y when they're combined into the BY bigram."
It would have been so awesome to not have that confusion. I've constructed enough puzzles with letter restrictions to realize how much the fill can suffer, especially when you choose not to use common letters, but Bs and Ys are a different story. It's a tough call — although BOOBY TRAPS has that confusion-generating first B, it's such a great answer.
Glad that Jon, Will, and Joel decided to eliminate PRESBYOPIC — even having worked in ophthalmic pharma development, that one only barely registered! I would have liked another example where BY weren't just the word BY, though, something like RUBY RED SLIPPERS or TRIPOLI, LIBYA. Alternately, having all BYs be separate words would have given nice consistency.
Excellent gridwork; just a few minor bits in IRED (odd form of IRE), RES, and GSA (General Services Administration). The theme constraint makes filling around those BY regions challenging, so the overall smoothness is even more appreciated than usual. And nice bonuses of CALIPHS, STONE AGE, MAESTRO, EAT DIRT, too. To do all that with so many entries affected by the theme is a fantastic result.
Another really clever idea from Jon. I felt like there was a little potential left on the table, but I still greatly enjoyed the solve — and perhaps even more so, the post-solve analysis. That's a great sign.