Long player choices are just cut off once they reach the end of the frame, with "..." shown. It should do a line break and continue the text below, only cutting off for much longer choices (maybe a limit on height instead ?)
Seems like the issue was fixed for Storyline (according to Ellypse), although I've not been able to find a specific commit so far.

When going from version 1.x to version 2.x of Storyline I rebuilt the dialog choices using widgets that dynamically adapt their height (and have nice animations, margins, icons, and everything, and the view scroll when there are too many options, unlike now). It would be interesting to use those widgets (although, the code can be way better now that I know my way around Lua, mixins, and templates more)