[tatersolid]

Written information clearly benefits from bold, italics, ordered and unordered lists, section headers, etc. Normal people don’t really understand text surrounded by underscores or asterisks (I never receive messages with those constructs from non-technical people).

Formatting lists or indented quotes (also common in “normal” email usage) using white spaces and other semi-arbitrary characters is tedious and brittle.

The “rich text” features of HTML email definitely improve readability and understanding when used with restraint.

[Fice]

It is useful to have a way to represent structural and semantic information in email text (paragraphs, headings, quotes etc.), but not custom layouts and styling — that should remain under full control of the reader.