Dan's post covers most of the basics but here are replies to the comments you left on the post itself.
To the DVoter: […]
Commenting about downvoters is never constructive. Just don't do it. For background on why downvoting works the way it does you can start with this meta post. Comments complaining about downvotes should be flagged as "not constructive" and will be removed on sight.
@Caleb Can you have the message attached to my answer removed, please?
First, you can't ping random people just by adding their name. The system only lets you ping names that have previously commented on or edited a specific post. Other names will just go into the ether. I didn't get notified about these comments at all.
Second, commenting isn't the right mechanism. If you need a moderator to review something (including having post-notices removed) use the flag link and follow the form. That way whatever moderator on duty is notified about the task. Please don't flag until after you've edited posts to address the issues.
If the DV was a part of some new automated process, then there needs to be an automatic warning prior to its implementation.
No, it doesn't need a warning, it is the warning. It is placed on posts that sort of but don't quite qualify as answers. It's meant to prod the user to fix the issue and (almost more importantly) let other site readers know that the post isn't a template to follow so they don't think it's okay to post similar material.
If the issues get addressed in a timely manner then the post-notice can be removed. If not, it's likely the post will eventually get deleted.
More egregious violations will just be deleted and can be un-deleted if the issues are addressed. Post-notices are a early warning system providing a grace period — there is no need for an early warning system for the warnings.
Lastly, no these are not automated; they are placed by site moderators. Generally this happens in response to flags on posts, either Not an answer or Very low quality, that moderators agree have some validity but not enough to delete outright.