Seeing as the minimum post length is (default) 20 characters
IMHO, as a poor typist, faster than 3 seconds is very fast indeed.
min first post typing time (default 3000)
Minimum amount of time in milliseconds a user must type during first post,
if threshold is not met post will automatically enter the needs approval queue.
Set to 0 to disable (not recommended)
auto block fast typers on first post (default checked)
Automatically block users that do not meet min_first_post_typing_time
Admin -> Logs -> Staff Actions does have the “block_user” action, but there are some problems.
The result set returned in the UI is truncated and although it can be “filtered” to remove “extra stuff” I know of no way to initiate filtering other than by clicking on what is available in the results the UI displays.
It is likely possible to use the API but I haven’t looked into to trying that so I don’t know.
I do know you can run a CSV Export that will contain everything eg. This one I Blocked directly from Admin Users using one of my aliases on a newly created account (BlockedGuy1)
staff_user, action, subject, created_at, details,context
AdminGuy1, block_user, , 2016-02-18 05:48:30 UTC, ,