If you navigate to MY_WORKSPACE.slack.com/stats#members you can see "Messages Posted" for each member like this:
If you export the data as a CSV, the column is called
How is this number calculated? I assume it includes all messages to channels. Does it include direct messages? I assume that reactions (e.g. a "thumbs up") do not count toward this number.
I read through https://get.slack.help/hc/en-us/articles/218407447-view-analytics-and-usage and https://get.slack.help/hc/en-us/articles/220556107-How-to-read-Slack-data-exports but couldn't find the answer.