Howdy — following the migration to UCP, we're aware that there are a few issues with comment sections on some articles.
The issue seems to be affecting some of our larger articles with thousands of comments — if I recall correctly, those articles have in some instances 20-40k comments. The issue means that comments don't appear at the bottom of articles, meaning that users cannot comment, or see older comments; an error is shown, and refreshing the error does little to solve the issue.
Staff are aware and are investigating the issue. I assume that it will be fixed some time in the near future, but if anyone sees any further issues with comment sections on articles, please do let us know on this thread!