I thought it might be easier to ask rather then plow through the code to discover how the element is derived.
@douglasrfix quoting the specs:
from field (optional) denotes the author of the message. This is the peer who initially authored the message, and NOT the peer who propagated it. Thus, as the message is routed through a swarm of pubsubbing peers, the original authorship is preserved.
Thanks. Got lost in the various docs twice and then called for help before I drowned.