From this file:
https://github.com/esoui/esoui/blob/...ingeditbox.lua
I found the following function's line:
Lua Code:
local displayText = self.shouldEscapeMarkup and EscapeMarkup(text, ALLOW_MARKUP_TYPE_COLOR_ONLY) or text
Maybe the EscapeMarkup function helps somehow. But I guess the AllowMarkupType in the XML should be best.