If it’s a critical error, the only workaround I can think of would be to have the user create a new post for the correction. If they do that, any users who are watching the topic or the category will receive an email notification about the edit.
For most cases, the email time window mins site setting is intended to handle this issue. Its default value causes a 10 minute delay from the time a post is saved until email notifications are generated for it. Hopefully that gives users a chance to edit any obvious errors in their posts.