My guess is that many people would assume that the parameter is applied in the default config sourcenat rule with action=accept when reading the MT file.
I don't think I understand what you meant here.
I dont believe many would think If there is no action parameter then we should assume there is actually an invisible action parameter in effect with an action of accept.
Any rule has some effect. Any rule consists of filters, which define what packets this rule should be applied to, and action, which defines what to do. Both filters and actions are defined by the corresponding parameters. And the
action parameter is not the only parameter that defines action. For example the
to-addresses and
to-ports parameters also define/shape action. When some parameter is not specified it is either an error (when no reasonable default value exists/defined) or the default value is applied (assumed). There is nothing unique to RouterOS here.
on verbose are usually displayed also default values not exported with compact, but in this case... nothig....
Well, I would probably consider this an
export bug.