Yes, comment submitting is rather slow. Somehow slower that it used to be tough I might be wrong and there is some problem with my site.
Most comments on my site are added between 5 to 10 seconds but sometimes they really get stuck. Example:
POST https://marzycielskapoczta.pl/wp-comments-post.php 302 Found 1m 6s
GET https://marzycielskapoczta.pl/1-gz-zdobywcy-nibylandii/comment-page-1/#comment-236370 200 OK 1,24s
Usally it’s:
POST https://marzycielskapoczta.pl/wp-comments-post.php 302 Found 8,94s
GET https://marzycielskapoczta.pl/zespol-szkol-integr...nowicach-slaskich/comment-page-1/#comment-236378 200 OK 916ms
[WP-Ajaxify-Comments] Comment has been posted
[WP-Ajaxify-Comments] Found comment URL 'https://marzycielskapoczta.pl/zespol-szkol-integracyjnych-i-szkola-podstawowa-nr-5-w-siemianowicach-slaskich/comment-page-1/#comment-236378' in X-WPAC-URL header.
[WP-Ajaxify-Comments] Found unapproved state '0' in X-WPAC-UNAPPROVED
[WP-Ajaxify-Comments] Anchor '#comment-236378' extracted from comment URL 'https://marzycielskapoczta.pl/zespol-szkol-integracyjnych-i-szkola-podstawowa-nr-5-w-siemianowicach-slaskich/comment-page-1/#comment-236378'
[WP-Ajaxify-Comments] Scroll to anchor element Object[article#comment-236378.comment-article] (scroll speed: 500 ms)..
If you want to test it, you can spam comment my site (I have moderation enabled).