I don't see it on my personal laptop on Firefox (Linux Mint), or on my workstation at work also using Firefox (Ubuntu 14 - no plugins).

Edit:

WOW I can't believe this, I opened it up in Chrome and it works / shows the comment folding option. It astounds me how much Chrome is becoming the new IE in regards to functioning websites where I wont be surprised to see (or not see) more cross-browser issues when using Firefox instead of Chrome.

Can I have the web where everyone wanted to be backward compatible with all browsers back?

Edit 2:

Also wondering how this got published by Reddit and nobody noticed some basic site functionality missing?