I love that Squarespace supports Markdown. I hate that it does such a piss-poor job of it.
If you've ever tried to paste more than a few paragraphs of Markdown-formatted writing into a new Squarespace post, you've probably experienced jumpy windows, weird clipping and scrolling behaviors, and all other manner of nonsense. I don't know what the issue is, and I got tired of dealing with it.
My new workflow is Author Markdown in TextMate or nvAlt → Preview text in Marked.app → Copy Rich Text (⌥⇧⌘+C) → Paste rich text into "Text" (not Markdown) block in the Squarespace editor. Goes in without a hitch, links and all.
Now, if anyone has tips for weaving images into a long text post after the fact, I'd love to hear them.