By default, all users who are assigned a profile that has the feed post editing permissions enabled can edit their posts and comments. If needed, you can disable feed post editing for all users in your organization, regardless of their assigned user profile.
We can also shut off post and comment editing for all users assigned the “Can Approve Feed Post and Comment” permission.
The feed post editing feature is disabled for your entire organization (or, for step 5, for all users assigned the edited permission set). Users can no longer edit posts and comments.