Thank you for the reply.
I did see these links. They come up as first suggestions when entering this question. The EOF newline answers do not seem applicable as (1) I am feeding a string to markdownify, no newline, which creates the space, (2) I checked, and the partial does not have the new line at its EOF. All template components already have the {{- ... -}}.
I shall still find out what the render hook is and what to add.