If I enter an invalid URL at the login form, I expect to receive an informative, helpful error message that informs me why I'm not able to log into the app.
The following error appears if I enter an invalid URL at the login form, which isn't that helpful to users:
"Couldn't connect to WordPress site. There is no valid WordPress site at this address. Check the site address (URL) you entered."
Screenshot:

This was raised by @jtreanor and some other recent support rotations as a lot of support requests are made up of users who enter an invalid URL. More informative error messaging could have a positive impact on the number of incoming requests.
iOS version of this issue is here: https://github.com/wordpress-mobile/WordPress-iOS/issues/10294
Ran into this in #1648733-zen, where the user had entered the URL "Santara Net Review".
It would be great to produce an error that states this isn't a URL, and gives an example of a URL.
Another in #1666486-zen - the user entered "La vie d'una Maison"
Looks like some folks don't understand they need a "domain.tld" format for this to work. They're entering the name/title of their site, instead.
Here's another who entered "Estanislao Mallofre Jane". #1749121-zen
Another example here in #1834758-zen

Another case in 1899497-zen. They've entered an apparently random sequence of numbers and letters.
Another in 1923800-zen. Again, a random-looking sequence of numbers and letters.
Raising in priority due to the number of user reports referenced.
Thanks Sheri!
I ran into another of these today in 1949634-zen.
Folks seem to think they can just type in relevant search terms.
I blame Google 馃槅
I have made a design request for this and already received some tips. I also requested a copy for it. Once I get the copy, I'll open a PR for it.