title: adding horizontal rule to html rmarkdown doc hides sections of text
body: <p>I am making an Rmarkdown document that knits to an HTML page. Instead of separating some text sections with headers or bullets, I just want to draw horizontal lines between them.  </p>
  
  <p>According to <a href="http://rmarkdown.rstudio.com/authoring_basics.html" rel="noreferrer">http://rmarkdown.rstudio.com/authoring_basics.html</a> this would be called a "horizontal rule" and I can do that with three or more <code>---</code>. However when I actually try to do this, various sections disappear from the html doc. Here is a very simple example of my code:  </p>
  
  <pre><code>---
  title: "formatting issue"
  author: "rrr"
  output: 
    html_document:
      toc: true
      toc_depth: 2
      toc_float: true
  ---
  
  ```{r setup, include=FALSE}
  knitr::opts_chunk$set(echo = TRUE)
  ```
  
  # bla {.tabset}  
  
  ## tab 1  
  
  ---  
  **text1**  
  bla  
  
  ---
  **text2**  
  bla
  
  ---
  **text3**  
  bla  
  
  ---  
  
  ## tab 2  
  
  bla
  
  ## tab 3  
  
  bla
  
  # bla  
  
  bla bla bla bla
  </code></pre>
  
  <p>Notice that text sections <strong>text1</strong> <strong>text2</strong> and <strong>text3</strong> do not all show up when you knit to html. When I mess around with it, I just end up with different ones missing or not, but I can't get them all to show up or figure out why. </p>