From CoriS on the forums:

Just another thought ... I wondered if the snippet window has a font-choice, or whether people will be using their default browser font. DP has a famously-ugly in-house font, which does distinguish quite well between commonly confused letters (e.g. b and h.) However, it takes practice to use it, and it does slow down the reading somewhat, so I don't think we could easily inflict it here. But perhaps a monospaced font?