Limited on purpose
Palm is constrained on purpose. For the most part, it's meant for writing, not for building complex websites. There are some basic formatting tools <b>, <em>, <u>, <blockquote>, <ol>, <ul>, <a>, <img>.
View source philosophy
The ability to "view the source" of a website is a beautiful part of the web. When Palm edits HTML, it makes it human readable so that you and others can view the source and easily understand the HTML behind each page.
WYSIWYG
Yes, Palm is a WYSIWYG editor. HTML is beautiful but it's also a barrier for people not yet familiar with making websites. Palm aims to bridge that gap. You can use Palm to write HTML and view the source to learn how HTML works.
CSS
Palm is not a CSS editor, but you can always customize your Palm site's style.css in a code editor.
Images
Palm supports the <img> tag. You can either click the image button or drag & drop an image into the editor. Images will be resized (1500x1500) and saved to an images directory. Image support is somewhat experimental and alt text support is still in the works.
Can I add Palm to an existing site?
You can always try. You will need to add #editor to an element on the page so that it knows which part of the page to pull into Palm. Warning: Palm might remove any custom HTML inside your #editor element. It's best to write and format within Palm to avoid this.
Why is it called Palm?
A dual meaning, referencing a portable writing device from the past and, well, it's about writing with your hands. A homage to a simpler computing era, when everything wasn't so glossy and visually heavy.