Defaults to "Off" ("No") and can be set per-sub-board to either:
- "Yes" parse/apply markup style to displayed message text while still displaying the markup tags
- "Hide" parse/apply markup style to displayed message text and hide (don't display) the markup tags
- "No", treat marked-up messages the same as any other message text, same as before.

The supported Markup tags at this time are:
#bold text#
/Italicized text/
_underlined text_
#inverse text#

Now, ANSI-BBS terminals (and Synchronet) do not support the concept of italic or underlined text (at least, not yet) - so those styles become combinations of the blink and high-intensity attributes which can be used to choose alternate fonts and this works well.

These 4 styles were chosen to be compatible with GoldEd's "Style Codes", though GoldEd is actually very configurable in its support of these tags/codes and its possible we're not 100% compatible. For example, GoldEd (and SemPoint) both support the combining of tags/codes to created combinations of styled text - Synchronet does not (this is consistent with Mozilla/Thunderbird's "Structured Text").

Multiple words can be styled with a single set of tags, but the first and last word must be delimited by white-space (this is not consistent with Markdown).

Multiple lines can be styled with a single set of tags, but not multiple paragraphs (this is consistent with Markdown).

The rules I chose were to minimize false positives but maintain some interoperability with GoldEd and Thunderbird with a familiar/common tag syntax.