I like to use this style of italics for keywords. (That's also what the Maple examples do.) My thinking is you see keywords so often that you recognize them by shape, not by reading the individual letters. And my theory is that the italic variant being a little harder to read helps my eyes skim over keywords, to focus more on words that I do need to read precisely, like variable names.

It does mean that I spend some time customizing my syntax highlighting theme to make it work the way I prefer. I've got examples set up on my blog. Although that's not Maple - it's a different font with cursive italics called Cartograph CF.