I bowl in a league that gives open play credits for split conversions, clean games, and certain scores like 33 in the 3rd 66 in the 6th, and 99 in the 9th.  Last night I was clean going in to the 10th.  I struck my first ball, left a 4-6 on my second ball, which I did not convert.  Did I have a clean game?

Have to agree to an extent with Steven here...I disagree with his personal view on the referenced 298 even though the 8-count was a split although I agree that avabob's game is not one I would personally view as clean.  I'll explain reasoning for both...

avabob struck on the first shot in the 10th, thus yielding the additional two shots.  As we generally consider 'clean' frames to be clearing the deck in one or two shots, I personally would not consider strike-split to be a clean 10th frame.  If you strike, then you either need to go strike-count or else spare in those next two shots...but again, this is MY view and how I personally would view the accomplishment.

As to the 298 game ending in a split, I would still view that as a clean, albeit disappointing game precisely because there were two marks in the 10th and the split-8 is effectively no different than if someone had gone XX8 or any other XX6 (or better).  I'm old school and view a five count on a mark to be a loss of the mark, hence my use of 6 or better.  The loss of the 300 would be frustrating in ANY circumstance, no matter HOW many one may have thrown, but to say the frame was open simply because the third shot (of a maximum three in the 10th) was not a strike just rings hollow for me...it is, after all, the second shot of the two you are awarded for a strike on the first shot in the 10th.

And with that, I return to my little retired-from-the-game corner...

IUSBC rules are intended to be black and white (or as much as possible).  The rules are sometimes written in a way to prevent interpretation for ease of enforcement.  So trying to change the definition of what a clean game is goes against the USBC intention.  Sure, one can personally think they didn't have a clean game in their mind by not sparing after a strike in the 11th/12th frame, but to everyone else that must be considered a clean game.  Perhaps others will side with you and agree it isn't a clean game, but saying it isn't is similar to saying a strike has to have all the pins off the deck.

 
I don't disagree with much of your analysis. As I've stated repeatedly, I understand the USBC definition of a clean game, but I personally don't agree with it. I'm not trying to interpret the USBC definition any other way than it's stated and have no expectations that it will ever be changed. Anybody can keep their 'clean game' with a blemish without fear I'll come after them  .
 
The only issue I have with your analysis is comparing the standard for a completely clean game to a strike that has to achieve certain style points. One is absolute and easily measurable while the other is subjective. It's comparing apples and oranges.

Why is the last ball referred to as a fill ball, not the last two balls in the tenth?