not yet, but I think of a delayed shell script (cron 15min?). JS (clientside) may be not of much use.
Or use a feedback webform via https://github.com/mro/form2xhtml - doesn't have to be email then.
Or monitor IMAP folders for accepted comments and cron them to the webserver a la https://codeberg.org/mro/flohmarkt.monte-ts.de/src/branch/ma... and online.sh