Having a good website template helps your website performance substantially (> 10%) by speeding up the site and making it more mobile-friendly. Mobile-friendly websites have been important (including for low-bandwidth users on any device) and feasible since the late 1990s with CSS. As Google has moved to a mobile-first web crawler, the important of being mobile-friendly is of critical importance for virtually all websites. Using appropriate layout elements in the page help your visitors and search engines understand the content better, boosting engagement rates and SERPP (search engine results page position).
The Wordpress Markdown syntax reference applies equally well to Jekyll and other website renderers that accept Markdown input. Almost 100% of website presenation can be done with Markdown.
Only use HTML directly to draw text arrows ↔, give detailed control of a few percent of images, and highlight text (e.g. red warning text).
Liquid generates almost all figures, table of contents, and image galleries.
HTML5 math character: Math characters directly in HTML5 Not all of these work in Jekyll Markdown, test them in the local preview first.