Custom code fonts and other options not working

First of all, clicking the UI buttons to change options doesn't seem to do anything at all, I have to manually change the 0s to 1s in the code.

Then, in order to actually change the font, I have to add the classes .react-code-text and .comment-body pre to the custom code font styling. .blob-code-inner doesn't seem to reference anything at all. This may be the case with the other options as well, but I'm not even sure what they're supposed to do, so I can't tell if they're changing anything or not.

Start by reproducing the UI button interactions and inspecting the selectors mentioned: .react-code-text, .comment-body pre, and .blob-code-inner. Trace why the options remain unchanged and determine which selectors the custom code font should affect; done means the controls visibly change the options and the font styling works without manually editing 0s to 1s.

Written by the indexing model from the issue text.