Attempting to use the site with a Nexus 4. I came across a question that was a duplicate, so I found the dupe and voted to close.
The only problem: the button is at the bottom of the modal. While in mobile view, that means lots of painful scrolling all the way through the question and its answers.
On the normal site this isn't an issue:
...but on the mobile site...
Here's an example:
This definitely affects usability while on mobile.