What happened was interesting and unexpected. I was building on top of an application (call it H) which had the DOM trees to manipulate, and JS to manipulate it

What happened was interesting and unexpected. I was building on top of an application (call it H) which had the DOM trees to manipulate, and JS to manipulate it with. I was reporting new bugs in H continuously, 1 or 2 every day. Because of the abstractions I'd done (it wasn't only tree iterators) I could largely work around the bugs invisibly - I pushed the bug-special-case-handling code down to make it invisible when using my abstractions. That made it all too viable to continue using an crappy, flaky product far longer than would have been possible - or sensible - without those abstractions. I'd turned the abstractions' value into a liability! I finally told them it wasn't worth continuing with H, they junked it AFAIK and I walked away.