Textpattern CMS includes a number of functions to reduce the prevalence of comment spam on your website. One of these is a cross-check against one or more known spam-producing IP block lists. A check takes place when a comment is submitted, and an additional check takes place when comments are subsequently rendered. If a spammer leaves a comment which tallies up with an IP from a known spam source on the block list, the comment will not be submitted. If a spam comment does creep through, and I can tell you anecdotally this is rare compared to other content management systems, then it can be marked as spam in the administration side of Textpattern.
I’m telling you this because there are occasions when this spam checking does impact the loading time of individual Textpattern articles, especially where there are many comments attached. At the time of writing, spam checking is enabled and uses the Spamhaus Spam Block List (SBL). In normal operation, leaving this setting as-is is absolutely fine, but if you do encounter slower-than-expected performance where individual articles are being shown or if users report a longer-than-expected time to preview a comment, try removing the block list check.
To remove or modify the spam block list check, log into the administration area of Textpattern and go to Preferences → Advanced → Publish → Spam blocklists (comma-separated). You will see one or more block list addresses; the default at the time of writing is `sbl.spamhaus.org`, though if you’re maintaining an existing Textpattern CMS administered by someone else, the contents of this box may differ.
If you only have `sbl.spamhaus.org` listed and you’re encountering individual article slowness, remove it. If you have additional block lists specified, remove them and leave `sbl.spamhaus.org` in the first instance; if that doesn’t help the loading speed of individual articles, remove the `sbl.spamhaus.org` reference as well. If you’re still having performance instances, read up on diagnosing Textpattern performance problems for additional advice and help.