[Recursing]

Seems to be just unicode in a code block. mv is 𝑚𝑣

[acqq]

And the verbatim lines are explained here:

https://news.ycombinator.com/formatdoc

[abrowne]

And two black squares on Firefox beta on my Android 5.1 phone.

[barrkel]

Works fine in Firefox Beta (and normal Firefox) on my Android 8 phone.

[abrowne]

OK, so fixed in up-to-date Android or with a better vendor (mine is TCL [Alcatel branded]).