Presenters leave invisible debris behind
Many decks contain phrases that made sense on stage but add no value in text: repeated section openers, one-word transition slides, presenter reminders, and visual-only labels. A converter can extract them faithfully, but that does not make them useful. If you remove obvious stage artifacts first, the Markdown becomes easier to search and easier to reuse.
A short cleanup pass pays back quickly
Before exporting, merge duplicate title slides, delete empty divider pages, rename vague charts, and turn screenshot text into actual text where possible. The goal is not perfection. The goal is to hand the converter a document that behaves more like content and less like performance.