It says markdown is not to be used, but some clients do it anyways. I don't want tables and other major things that can look messy. I just want bold, italics, and underline at minimum. Google+ had that and I've been missing it ever since Google+ shutdown.
Discussion
Limited Markdown support like that would have to be defined in the Kind 1 spec.
Additional rich text formatting would be a perfect use case for a new event kind.
I don't think we need an entire new kind for it. Clients can choose to parse it and remove it or display it, like they do now.
Most interesting to me is that the markdown and HTML reference is only explicitly stated for kind 1.
Kind 0 in the same NIP may presumably have markdown or HTML or anything else needing parsed as long as its in the stringified JSON object. There are no restrictions on clients from parsing a kind 0 in this way.
Every other kind also allows HTML and Markdown and imposes no client restrictions