I have the same issue. Partly it's to do with vertical resolution - when zoomed (Chrome is telling me 125%) in enough to stop there being massive wasted space at the sides of the screen the PM viewer's send button is actually below the screen - and this is in a heavily stripped down Firefox with nothing but the tab bar and url bar. The drop down nature and the fact the forum seems poorly laid out for 1366x768 (2nd most common resolution after 1920x1080) make this more than a bit irksome for PMs of any length. Given that 40% of monitors according to the steam hardware survey are 1366x768 or smaller, this seems like a problem. Would it not be possible to bring in a system similar to Facebook where there is a drop down notification, but click on the conversation brings you to a new page instead? It's wholly unsatisfying trying to discuss economics by PM with Telec when I have to either zoom out or plug my laptop into a 1080p monitor to use PMs worth a damn. But good lord the writing on this site is tiny at 100% zoom rather than 110 or 125%. I don't care about blue space, I really don't.