Rayat Rahman, when pondering how he can contribute to Calva, decided to pick up an extra important and super extra difficult task: Making Calva’s Paredit aware of, and honoring, multiple cursors. Multi-cursors is a super power in any editor, as is Paredit. The combo is mind-blowing.
Rayat is making super good progress and I am now using the builds from his PR branch at work, where the slowdown that the shrinking amount of quirks are causing is greatly outbalanced by the new powers I have when editing the code structure.
You find the latest builds with this feature here:
https://github.com/BetterThanTomorrow/calva/issues/1662
There you’ll also find instructions on how to participate and how the bug repports should be crafted to make it easy to act on them. We have tried to make it easy. The builds contain a new diagnostics feature that will let you translate the current editor state to the mini-language we use in unit tests: Calva Document Text-notation. I recorded a video where I introduce this tool and the text-notation language:
We haven’t found a way to implement this in small steps. (There probably were approaches we missed, but that ship has now sailed.) It’s a huge change, needing a lot of testing. When using it for work I seldom have time to document the quirks as I stumble across them, so this is a call for assistance in assisting Rayat with testing. Pretty please consider! 
A way to approach it is to just use the builds, then use the tool as you find bugs. Another way is to use the Guide to Calva Paredit and go command-by-command, making sure they still work. And also check that they work with multiple cursors.
Happy beta testing! 