If a URL ends at the right margin of the terminal, followed by a new line, the word selection logic knows that the line ends there, but the regexp matching logic doesn't.  Try:

perl -e 'print "http://", "x" x 72, "/\n", "zzzz\n"'

(assuming 80 columns) you get something like this in the output:

http://xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
zzzz

Now treeple-clicking on the first line doesn't select the second, knowing about the hard line break, but hover over it and see that the second line is selected as part of the URL.