The datamethods.org site allows participants to include a variety of information in their posts and replies. Here are a few of them.
Links to Web Resources
Use the notation [link description](https://...) as rendered here: R2
When sharing a large number of files, you may want to link to, for example, the base directory of a Github repository.
Equations
Use \LaTeX notation surrounded by $ ... $, e.g., $\alpha_{3} + \beta X^{3}$ to get \alpha_{3} + \beta X^{3}.
Code
To use a special font for software components, surround the name in single back ticks. To include a code block, put a line containing three backticks by themselves before and after the code block, as was done here.
require(MASS)
x <- 3 # this is a comment
You can also put > (greater than following by blank) before each line as was done here:
require(MASS)
x ← 3
y ← 2 # a comment
You can also highlight a block of code and click on the block quote icon to insert the two characters.
Tables
See this tutorial.
Attaching Files
Click on 
You can upload image files, html, pdf, and R binary rds files. Here are two example uploaded files.
r2.html (10.1 KB)
condprob.pdf (45.1 KB)