[tmail21]

Agreed that all of these can be used asynchronously. However, I would refer to these as "incidentally-asynchronous", in the sense that their design goals were not primarily to be asynchronous (and hence support "Deep Work").

The major determinant of asynchronous deep collaboration efficiency is number of "cycles-to-outcome". (where a cycle is roughly a request/response loop).

Email because of its lack of shared state collaboration generates lots of extra cycles because of confusion on shared state (i.e. attachment nightmare).

Conversely, something like online document collaboration supports shared state collaboration, but is really poor at "what happened". For all but the smallest of documents this leads to compounding "implicit document rot" on every iteration. Alternatively, it leads to ever increasing time to "catchup" once again vastly expanding cycles-to-outcome.

Neither is good with accountability (something that issue trackers are good with). Lack of accountability is another driver of increasing cycles-to-outcome.

A deep collaboration solution that enables Deep Work could be designed from first principles based on minimizing cycles-to-outcome.