I'm using Marked Quick Look 1.0.3 (9) on Sequoia 15.7.7 (24G720). When using Finder in Column mode, and I hit space to view a Markdown (.md) document, it doesn't always fill the pop-up window properly. It might be related to having Finder Preview (next column) active. When I click on the file, the Markdown preview shows properly in the preview column. When I hit space to open pop-up QL window, the preview col is greyed out (probably by design). But in the pop-up window, the preview seems to be rendering at the same width as the preview column was at, not at the full width/height of the pop-up window.
Related: When I hit space again to close pop-up QL window, the Preview column to right is still greyed out. I have to unselect and reselect file to have it refresh/update.
Video showing (mis)behaviour:
https://drive.google.com/file/d/1SD4KoUd1yS5rSQBkuvIhQJY3tJB1ZFqk/view?usp=share_link