The message field in the RulesAction plugin does token replacement, based on the entity provided in the "Data" field.
We should also allow token replacement for the Room field.
The use case for this is for an issue tracking system, for example a system built using Organic Groups or Group module, to post a message in a Matrix room that follows a particular alias pattern.
Closed: won't fix
1.0
Code
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
Unless somebody wants to step up and contribute this, I won't be working on it -- we're now using ECA instead of rules.
The new ECA plugin supports tokens already -- if you need this functionality, I recommend switching over to that.