I have the same issue with comment_formatter.ERROR: and don’t even have comments from discourse turned on, nor ajax. It hits the logs ever 2 seconds round the clock. Meanwhile a lot of slow PHP processes and an FLOCK that halts everything, bringing the site down repeatedly.
script_filename = /www/index.php
[0x00007fa5ef613c90] flock() /www/wp-content/plugins/wp-discourse/vendor_namespaced/monolog/monolog/src/Monolog/Handler/StreamHandler.php:106
[0x00007fa5ef613c00] write() /www/wp-content/plugins/wp-discourse/lib/logs/handlers/file-handler.php:167
[0x00007fa5ef613b50] write() /www/wp-content/plugins/wp-discourse/vendor_namespaced/monolog/monolog/src/Monolog/Handler/AbstractProcessingHandler.php:34
[0x00007fa5ef613ad0] handle() /www/wp-content/plugins/wp-discourse/vendor_namespaced/monolog/monolog/src/Monolog/Logger.php:283
[0x00007fa5ef6139b0] addRecord() /www/wp-content/plugins/wp-discourse/vendor_namespaced/monolog/monolog/src/Monolog/Logger.php:614
[0x00007fa5ef613930] error() /www/wp-content/plugins/wp-discourse/lib/discourse-comment-formatter.php:62
[0x00007fa5ef613670] format() /www/wp-content/plugins/wp-discourse/lib/discourse-comment.php:310