Ricardian contracts should be presented to the user before calling an action on a contract. For that purpose place holders can be used.
Which place holders are supported by which tools in which syntax?
The question is not about the contracts (that are written in mark down) but about the place holders in these contracts.
{{ signer }}
e.g. in github.com/eoscollective/eos-ricardian/blob/…{{ param_name }}