Boost is based on Old Reddit markdown parser which is close, but not identical to the one Lemmy has, and there are some edge cases and compatibility issues.

FWIW, the GFM extension used for Markdown tables defines that a newline should be required for a table to function:

You must include a blank line before your table in order for it to correctly render.

But as an app for browsing Lemmy, Boost should match whatever Lemmy does, even if it does things “wrong”.