Discourse AI bases spam scanning is not vulnerable to this.
Additionally, we do have safeguards that stop people from editing once a post is old.
If this is reproducible we need a bug report, we would love to fix it.
At this point in time I consider Akismet as incapable of dealing with the current pattern of spam online, it has too many false negatives.
Discourse AI has been doing very well, you can configure it on your self hosted instance for free if you lean on a model such as Gemini Flash 2.0 which does a spectacular job with spam.
Can you try it out and report back?