When llLoadURL is called, the dialog in the attached image shows up with the requested URL and the buttons to either open it or cancel. When clicking the "Go to page" button, the URL is loaded correctly.
But the UI automatically adds the "?" at the end of the prompt into the hyperlink. The ? character in the screenshot wasn't included in the URL passed via llLoadURL. Thus, if the user clicks the hyperlink instead of the button, the URL is loaded in the browser with an additional ? character, which can cause problems if the page doesn't expect the ? character.
I'm reporting this on behalf of a customer who experienced this issue; I don't run Singularity, but Firestorm addresses this behavior by adding a space at the end of the URL so that the UI doesn't add on the ? character into the hyperlink.