This question already has an answer here:
- Mathjax/markdown issue 2 answers
The following text is typeset correctly in a post, but it seems to be broken when posted in a comment. (Markdown somehow interprets left [ as beginning of a hyperlink).
Any concave function $f\colon[0,\infty)\to\mathbb R$ such that $f(0)=0$ is [subadditive](http://en.wikipedia.org/wiki/Subadditivity).
Any concave function $f\colon[0,\infty)\to\mathbb R$ such that $f(0)=0$ is subadditive.
I'm posting two comments below this post to illustrate this. I've tried this also in Formatting Sandbox and here's a screenshot:
(Of course this is not very important and it should be easy to circumvent this, when you notice the problem. I just thought I should mention such behavior here at meta, when I ran into it.)