Thanks for the feedback, everyone. I wish I had a better picture of what's going on out there. My impression is that people shy away from using smart phones for discussion boards, and even email, preferring text messages. They prefer devices with larger screen sizes like computers for discussions and email, but computer sales and, I assume, computer usage rates are down. If my children and their friends are any indication, email usage by the younger generation is significantly diminished.
Computers aren't going away. Office workers must only very rarely use their smart phone to do their work - they must almost always use computers. But I think fewer and fewer people have computers at home, and those who do are using them less often.
So what's this mean for discussion boards? My own view is that decreased participation here at EvC merely reflects an overall trend in the way the Internet is used. More and more people are using smart devices. And who surfs (explores) the Internet anymore? Most people probably go straight to Facebook or Twitter or Snapchat or any of the other major destination sites.
I think computers and to a lesser degree tablets will be the platforms of choice for discussion boards, which is how I justfity the decision not to put any effort into making EvC provide a satisfactory user experience on smart phones. I'm not sure it's even possible to provide a "satisfactory user experience" on a smart phone when a lot of typing is involved. For one thing there's all the different keyboard screens that are necessary. Typing "[qs]" on a smart device goes like this (this is for an iPad). Each quoted set of letters is a single keystroke:
This is, of course, absurd, but to get a different keyboard layout I would have to write an app, which I've decided not to do. It is the keyboard more than anything else that keeps me from using my tablet for EvC. I do have an external bluetooth keyboard, but it's just as easy to sit down at my computer as it is to dig out the bluetooth keyboard.
So I'll continue to develop under the assumption that the platform of choice for discussion boards is a computer.
I should mention that I did get a note from Google telling me that EvC was being downgraded on searches because it was mobile-unfriendly (text too small, buttons too close together, etc.), and I did make the text larger for mobile. I'll also try to make some other accommodations - being downgraded in Google search has to be taken seriously.