You didn't address my point; you criticize the low level of competency of OW courses, but a dive to 100 ft is, by definition, beyond the competency of an OW diver.
Not necessarily. Ive come across divers of that level who would be more than competent at that depth in those conditions. I've also come across others with more advanced certs i wouldn't let anywhere near it.
Is there no responsibility of the crew of dive boats to check the competency of their customers for a given site?
Hopefully not - whatever happened with personal responsibility. If people are adults let them decide what they want to do.
In this case, it's very simple: if you have no AOW card or higher, you either dive with a professional or you don't dive to 100 ft.
AOW card doesnt make you competent just as not having one doesnt make you incompetent.
What is the purpose of having these certification levels if people ignore them?
To make people feel better and provide guidelines about what sort of diving they're likely to be comfortable doing.
Letting her dive with her non-professional husband on a 100 ft dive was inconsistent with guidelines for her certification.
Firstly, they're guidelines. Nothing more. Secondly, how do you know the husband wasn't more than capable of accompanying the diver? Just because he hadn't paid an agency a fee to do another course doesn't make him a bad diver.
Personally, I would be a little wary of someone who worked a dive boat and who viewed a 100 ft wreck dive in a strong current as "not hard" unless someone had "crappy skills". Such machismo might induce people to dive sites beyond their abilities (come on, it isn't hard! or are you too crappy for this site?!).
The most important thing for anyone to do is for the individual to work out their own level of comfort and ability and dive to within that. People need to stop relying on other people to tell them. 100ft isnt very deep, visibility there is often excellent. It sometimes gets currents and chop. That's isn't difficult and shouldn't be difficult to anyone with common sense and basic skills.
How is someone new to a site, or to diving like Tina Watson, to know what is a "hard" dive?
The same way any of us do when diving a new site. You take local advice on the site, the layout, the hazards and make an informed decision based on your own skill level as to whether to dive it or not. A qualified diver should be able to appraise a site based on a detailed brief and decide if they feel its within their limits or not.
Where does a new diver go for guidance regarding their ability to dive a site?
If in doubt ask an instructor or someone with experience of the site. If still in doubt, pay an instructor to go with you.
Should she listen to her husband, who never did the dive and whose motives were unclear?
His opinion is just as valid as someone else. Why WOULDNT she ask?
Should she listen to Scuba Diving magazine (which rates it beyond her experience)
Basically no. Magazines are completely worthless for detailed site briefs and write articles to cater for the lowest common denominator of person the majority of which will never even go to that country yet alone dive it.
There isn't an operation, or a dive site, that can't bite the best of us in the kiester.
However with basic skills and common sense nearly all of those potential problems can be eliminated, reduced or coped with safely.