[chrisjj]

> I'd forego HTML entirely and either say it's strictly plain-text

Inferior to typical print media text richness would rightly get rejected by most users.

> or use some Markdown-like formatting spec that looks fine even when viewed as plain text

No rich format can "look fine" when reduced to plain text. Reason being that the reduction loses information that the sender relies upon the receiver seeing.

> The evils of HTML in email (phishing, impersonating companies,

Neither of those evils are specific to HTML.