I have a very mixed reaction to the post.
I don't know why you are so unhappy with your DM training, and there may be a great deal more to it than the two specific incidents. But it is definitely true that the goal of the instructor supervising your DM class is to produce someone who can safely assist with classes and guide dives, and if the instructors felt that your performance in general was consistently better than satisfactory, that there was no need to hold up your certification over nitpicky details.
True. You nailed it. There is much more going on here. Jeff signed up for the course which is taught in quarterly sessions, according to the owner, but then Jeff subsequently went on extended holiday half way around the world. The "policy" at Splash is that if you can't meet the schedule, you must pay for a private class. That detail caused the owners a bit of stress, and believe me they wanted compensation for their inconvenience. But even that is hardly the whole story. The Instructor (and co-owner) in question was motivated to process DM certs because of his need for a few more pro-certs for his upcoming Course Director slot. [Opinion Statements Removed] Interesting, if Jeff honestly seeks out remedial training, that will make 100% of the recent "graduates" trained under this instructor having felt under prepared. During the most recent go-around, many of the DM/Cs reached out to me privately for help and in some cases I snuck them into pools and worked on skills for free out of sympathy. For me, I had to make a decision about how I go forward as a professional, and my associations. I decided to make the most ethical decision for myself and my family. I learned a long time ago the guys doing it right, do it right when no one is looking over their shoulder. Jeff should make his own decision regarding additional training, but I must admit I'm disappointed I couldn't conduct his DM training sequence.
Regarding the overhead environment, I spoke to the student in question at length. Standing under a wooden pier that has four feet of airspace under it is hardly an overhead environment. Sounds to me like the Instructor who was managing the exercise should have yelled at himself. If an Instructor has two DMCs and an OW student doing a Nav exercise and you end up in the wrong place, who's at fault?? No brainer in my mind. The only dive professional actually present, in teaching status, and insured is the Instructor. Period. Yell at yourself, take the walk of shame, do whatever you need to do, but the feedback should have been, "See how easy it is to get turned around. Before you take a student, let's assure ourselves we're oriented, and we know the hazards". That's all that needed to happen, but the Instructor in question is more worried about asserting himself as the all-knowing, all-being ass at every opportunity.
I think this situation will self-resolve, as the customers are literally boycotting the shop and making sure they spend absolutely no money on gear, or training. As a land-locked dive shop, it's gonna be difficult to exist if every review you have on the Internet includes the word, "Shiesty", and you can't sell gear and/or Continuing Education.
I'm not sure Jeff's approach here was the most appropriate action, however he's certainly entitled to share his thoughts and opinions. Sadly, there's nothing new in this article, the comments on every review site about Splash speak for themselves and have for several years. You don't need to be Yelp'er to know what's up in just a few seconds. I'm sure the owner will instantly file some sort of legal action against Jeff for slander in a moment of hot-headedness - completely oblivious to source of the problem (despite having been told repeatedly, even in writing). So this is case closed, let's stop talking about diving, and start let's blow some bubbles!