This is a post written in plain Markdown (*.md) instead of R Markdown (*.Rmd). The major differences are:
You cannot run any R code in a plain Markdown document, whereas in an R Markdown document, you can embed R code chunks (```{r}); A plain Markdown post is rendered through Blackfriday, and an R Markdown document is compiled by rmarkdown and Pandoc. There are many differences in syntax between Blackfriday’s Markdown and Pandoc’s Markdown.