The line object outputs a bang when it has finished a ramp. When you instruct it to do the ramp in 0 milliseconds, no bang comes out. I find this behavior inconsistent. If you anticipate on the output of the bang for variable ramp times, you have to make an exception for time 0. Of course you can patch around it but that's not the point.
If it is not a big deal, and won't break existing patches (I guess not) please consider this a feature request.
I know you have much more important stuff to work on, but I wanted to ask it anyway. Thanks for listening.