Edit: some explaining; you open the 20 report tabs at once, and then close them as you send them
That's what I've been doing for a long time when I found a "batch" of bad posts, but I always have to slow down because of the 4 seconds delay.
I'd say, once a user reaches the minimum of 4 seconds delay, it should be removed entirely. On average, the forum doesn't allow more than one page view per second, so (apart from some burst space) that would be the new limit.
Indeed. If ever that they would lessen the 4-second limit, then I think it would bombard the system with reports and would take a long time for moderators to approve and review almost 60 reports for a min (if you wanted to make it a second limit). And 4 second is enough, even the 1 second request per page must also be enough, to somehow prevent crashing the system as well.
I've never tried using script for reporting batch spam post as I only report manually and would take 4 seconds per report by opening it in new tabs. Though scripting is convenient, the 4 second limit is I think fits if reporting was done manually hence enough time to submit a report.