My point here is exactly yours I think: best is not to focus on currencies that build on obligation or expectation of reciprocity, but simply on currencies that offer the possibility of reciprocity, simply by recording more formally what is going on.

Also, are you there yet?

You implement mutuality by finding out what the social agreements are for positive contributors or good citizens within a community which is able to share a resource of some kind. These resources may be stories, hash tags, “likes,” books, tools, or couches… but in each case, if you embody those agreements in the structures of a reputation currency, you enable the resource flows to cross boundaries of interpersonal unfamiliarity and scale of participation.

This establishes mutuality by enabling me to give freely to people because they are givers too, even if they are not reciprocally giving to me in this transaction or in any future transaction. Rather than direct exchange, it is an indirect benefit of increasing access to resources of all of us.  I may choose to receive from other parties that I don't have anything of direct value to provide to them, because they can also see that I'm upholding the social agreements (e.g. giving generously).  This assures that sharing and generosity is mutual even though it is not reciprocal.  It is also the way we naturally expect sharing in networks of trust to work.
It is worthy of noting that proper implementation of currencies which embody these agreements may in fact make it unnecessary to ever implement a medium of exchange currency, because they often operate MORE efficiently then monetary currencies to activate flows of resources and value.  My warning would be to not assume that exchange is always the desired goal. Adding additional complexity in terms of pricing and the kind of scarcity-based value measurement that accompanies it, may not add any benefits and may, in fact, stifle participation of folks who were previously participating out of fun, fellowship, generosity and goodwill.