In short, Robert Bringhurst says

• He does not object to starting a sentence with a word in small caps. He doesn't object to capitalizing a word in small caps, as long it is a word and not an acronym.
• He says that if I like guillemets, I should use them.
• He is not enthusiastic about concocted ligatures, and seems to indicate that other than for exact transcriptions, ligatures should only be used when the design of the typeface requires them.
• As for using typefaces to emphasize or pick out semantic distinctions he says that it would be best to consider the problem on a case by case basis.
• He did not seem to have much specific advice when answering Chris's question about typography in other mediums (especially for presentations or on the web).
• He thinks AMS Euler is a wonderful typeface design, but that it is incomplete in many ways (lack of proper kern tables, missing glyphs, etc.) and that the AMS should fund someone to produce a proper OpenType version.

I'll probably verify with him before too long that it he is fine with using more detailed excerpts of his response in a public setting.