There are some options to add comments in R Markdown file:
In RStudio, comment/uncomment lines with Ctrl-Shift-c:
<!-- Add some comments here -->
Option 2:
---
Add your comments here:
Paragraph 1
Paragraph 2
---
Option 3:
Hide text with:
r if(FALSE){" Add your comments here"}
Show text with:
r if(TRUE){" Add your comments here"}
There are 2 options to add small font texts in R Markdown file:
With <sub> + <sup>:
Normal text
<sub><sup>Small text</sup></sub>
<sub><sup><sub><sup>Tiny text</sup></sub></sup></sub>
<sub><sup><sub><sup><sub><sup><sub><sup><sub><sup><sub><sup><sub><sup><sub><sup>REALLY SMALL TEXT</sup></sub></sup></sub></sup></sub></sup></sub></sup></sub></sup></sub></sup></sub></sup></sub>
With <small>: <small>Small text</small>.
Ref: