They are more. edit: but they write or publish very much shorter responses.
Desktops are more usual when audience is more tech oriented. Otherwise… there is no point to do almost anything to bigger screens 
In northern Europe most of ”ordinary johns and janes” doesn’t have computer/laptop any more and they are using mobiles. That is world wide direction too and something that all devs and coders should remember.
It is not only issue of Discourse. Mobile revolution is reason why sidebars of WordPress is such waste of time — nobody sees them because it would need a mile lond scrolling.
And that is the main reason why forums can’t fight against some, Facebook, Instagram or fast messaging — you all can try to use screen and type longer message than two sentences
Am I now deep in off topic 
Again. Very good alternative to sidebar for chat is no sidebar at all.