Any paragraph indented with a tab is exported using $HTMLIndentedParagraphStart and $HTMLIndentedParagraphEnd. Normal paragraph markup is taken from $HTMLParagraphStart/End or, for the first paragraph, $HTMLFirstParagraphStart/End.
The default value for $HTMLIndentedParagraphStart is <blockquote>. In TBXs created pre-v5 the default was <p style="text-indent: 3em;">, to generate a modest indent.
Paragraphs starting with an asterisk (*) or bullet (•) are automatically tab-indented in Tinderbox but exported to HTML as bulleted lists.
Paragraphs starting with a hash symbol (#) are also indented in Tinderbox but export to HTML as numbered lists.
See more on automatic lists in Quick Lists.
Text set 2-3 points larger than body text ($TextFontSize) is exported to HTML as <h3>, 4-5 points gives <h2> and 6 or more points above body copy is exported as <h1>. Generally this is a useful enhancement but it can be problematic if the text size has been enlarged only for clarity within Tinderbox itself.
Assuming all text in a note is of the same size, but just bigger than the norm - e.g. in a 'readme' note - set the TextFontSize for the note to the same as the display size in the note window. As the text in now the base size (for that note) auto-headings are not invoked during HTML export.
These features are controlled via $HTMLMarkupText with ^text^ used to export $Text. If instead ^value($Text)^ or ^text(plain)^ are used to export $Text, the above effects are by-passed.