I agree that Courier is ugly and a bad thing to hardcode. I long ago switched to Lucida Console, which other than i and l is very close to the Mac/linux examples. I had forgotten that Courier was the default.
Ned, am I correct in thinking you would like this?
Mark, please submit a patch. Too bad that tk does not use something better for Windows too, but I agree that Courier is least bad here.
PS. Leave brackets off issue references like #20580 so they become links. The overlap is minimal; in any case, that issue will need several patches and subissues.