With that logic, why not remove the log in button to fit in a few more characters? I just think the trade off of having one single button appear and disappear on scroll to accommodate a single word is not worth it. Also, if a title is too long and getting the “more” ellipsis, the few characters that are gained from removing the sign up button will likely not make or break the context of the question. Lastly, it just looks silly/buggy when the topic title is short.
