Hi Polsteam,
As a professional in shipping business you should know the rights in professional business. And I think for professional business it is OK.
But here most shiplovers are hobbyists, who are retired or work in a different business. They do their hobby for their fun and not for business and do not want to deal with legal actions about photography.
If this, what you stated ist true, then our whole hobby on this site will be spoiled by legal matters.
And shipspotting to me is still a private forum (you have to become member) with the interest in sharing photos of ships despite the discussions after the swap to airnav. You can argue, if this a private forum than you can act as a private person showing your photo collection to your friend not in reality but in the web. So any photo could be posted.
But I would not fo so far. Concerning prints (which are copies of a negative) I act like you, I do not post any photo of my collection (which is quite big). But a negative does only makes sense to me, if I have the right to copy photos. Otherwise it is absolute useless, because much to small. So if I acquire a negative I do it for only one reason, to make copies of it (privately, as business with shipphotos does not interest me).
So members should be allowed to post scans from negatives they own until someone is reclaiming the copyright on that photo, which will not happen in my opinion as it is an unspoken law among private shiplovers, that an exchange of a negative means, that the exchange partner is allowed to make copies.
With digital photos it is more difficult as you only have data, which can be copied very easily and not real thing to talk about. I would treat digital data like prints, only post your own photos taken by yourself.
Kind regards from Bavaria and Happy New Year