@tomavatars I feel your pain! I thought the hardest part about the puzzle was going to be creating the bars and conditional formatting, but I spent 90% of my time on structuring the tables and getting filters and lookups to work. It didn’t feel that different from getting a complicated formula in Excel to work but understanding the nuances about the Coda syntax and objects was (and still is) challenging.
Regarding your =[Table].filter(Category=thisrow.Category).OscarWinner formula, I found that the column type of your current table matters. For instance, it looks like in the screenshot the “Category” column is a Text format, not a Select List or Lookup From Table. I experimented by changing the column type and found that Lookup From Table was the only option that allowed the filter formula to work correctly. This doesn’t make sense to me either since I believe as long as the text matches the lookup value, then it should work.
To add on to the complexity of knowing the column type to ensure your filter formula works correctly, I ran into the issue of using thisRow versus the column name as the reference (see this thread and related thread). Knowing thisRow refers to a tuple complicates things because there are instances where I think using thisRow by itself should not work (but works), and then instances where I think it should work (but doesn’t) depending on how you structure your tables.
As you said, much 
and 
to the team and community for attacking difficult problems.