[mbrock]

Most of my commits start with a component name prefix and a colon. I don't capitalize those. I still write literate English commit message bodies.

[jcrites]

That sounds reasonable to me.

  foo: Add utf8 support

If the component name is conventionally written in lower case, because it's a technical term, then I think a comment written in this way counts as good style. I might choose to capitalize Foo myself, but I think foo is defensible in that context.