The HTML plugin allows you to format text using HTML tags. The text you write is checked to be sure it won't interfere with other websites where it might appear.
See GitHub 
for plugin source.
This markup uses tags enclosed in angle brackets to enclose text to be formatted. The matching end tag includes a forward slash. A few tags don't expect to be matched with end tags.
Formatting
Use <b>...</b> for bold.
Use <i>...</i> for italic.
Use <h3>...</h3> for headings. By convention we use size 3.
Forms
Use <form ...> ... <input type=submit ...></form> for posts to remote services. Services are expected to respond with json for a page to be added to the lineup.
For example, this form submits an image url to a remote service as if the image had been dropped on an image transporter. See About Transport Plugin
Note: fidelity with the Transport plugin api is not required of form handlers.
We special case one action url and handle it within the plugin without transporting through a remote service.
<form action = "http://new_page/">
SVG
Scalable Vector Graphic (SVG) images can be embedded directly. We recommend specifying the width and viewBox attributes and omitting the height attribute to get the images to fit in our narrow pages: <svg width="100%" viewBox="..."
Authors can create internal links in embedded SVGs by providing a page title in the data-title attribute. In the example below we have linked this collection of pilcrow icons to About Paragraph Plugin.
<a href="/about-paragraph-plugin.html" data-title="About Paragraph Plugin"> ...