I committed to an Area 51 proposal (Science Fiction) and clicked on the Twitter icon to share the link with both of my Twitter followers. Once Twitter figured out I was logged in, it redirected me behind the scenes, and by the time it settled I saw that the text Area 51 provided was truncated at the ampersand in "Q&A." In the address bar I could see that the
%26 in the Area 51 link had been expanded, somewhere along the line, to an ampersand.
Upon further experimentation this looks like a bug specific to "New Twitter" (which I had enabled in my Twitter account); when I reverted to "Twitter Classic" and clicked on the Area 51 proposal-sharing link again, I saw the full text in the box.
It may not be possible to fix this from Area 51, but I wasn't sure where else to mention it.