Just two notes to anyone using this workaround.
Firstly, @jarlebh has now confirmed that he indeed isn’t doing any more work on the Tellstick binding, at least not as it looks now. That might mean that the binding will not be fixed at all, so this temporary workaround might turn out to be a permanent workaround.
Secondly, after a change in 2.4.0 Milestone 4, this workaround won’t work any more if your Items are still linked to broken Tellstick Things (as mine were), so you have to unlink the Items. For more info about this see What is ItemStatePredictedEvent?
edit: Or, as I have learned now, if you trigger the rule on received command instead of changed (and also change triggeringItem.state to receivedCommand) everything works even with the links in place. Updated the first post according to this as well.