Performance issue on lists of links

[jasonm23]

I have a page of approx 118 links / list items, and markdown-mode becomes grindingly slow when I go to edit the page.

Expected Behavior

Snappy, responsive edits on markdown pages.

Actual Behavior

approx ≥ 500ms lag on MOST edits.

Note: Except inserting a newline. Cursor movement and other read-only ops seem unaffected.

Steps to Reproduce

- [Name](https://example.com)
# copy the above 118 times, and edit the page, observe performance lag.

Backtrace

n/a

Software Versions

• Markdown Mode: From Git 2.6-alpha c765b73
• Emacs: 29.1
• OS: macOS Monterrey 12.6.9 (21G726)