Er, yes, well surmised
Done. And it all seems to work correctly now!
Of course, this is a case of RTFM, as the relevant pictures on the EmonTx - ESP8266 page clearly show the ESP8266 output isn’t connected…
I had wondered, in an exasperated sort of way, why the temperature output of the EmonTx had stopped. As you say, probably randomly reconfigured by the ESP, though the chances of sensing T0 1 seems slight … maybe a sign I should buy a lottery ticket.
As a suggestion for a small bit of extra info on the site, it might be worth adding a short sentence about this issue here or here… The latter link has a long thread about various ESP8266 issues, and this thread might be better there as well…
Thanks again @Robert.Wall 