Nah, that’s on me. But it’s not particularly relevant because you haven’t read the topic in that screenshot. If you had, you would have been prompted to sign up. JIT means just in time and those messages pop up contextually.
I guess what I would point out here is that after 10 years of Discourse, this is the first time I have really heard this discussion so I guess it’s either not a problem for others or they have edited their site text accordingly.
I don’t mean to sound dismissive, but we generally work to a rule of three.
Here is an example where there is a clear call to action “ask a question” that a user sees when they hit a mobile page on stack exchange and they are not logged in. Also they support both the signin/login as well.