There are no unanswered questions. Wait staff in France (including St Martin) are paid a wage, unlike wait staff in US who may, depending on where they are located, be getting only a little more than $2 per hour. In US, restaurant wait staff almost always are specifically called tipped employees. To be "fair" to US wait staff, you need to leave a tip in the range of 15%.

In France, wait staff are happy to get tips (of course!) but it is NOT necessary to tip them to be "fair" to them as it is with tipped employees in US.

Do you really expect an owner or manager of a restaurant to post on a public site (or respond to an email from someone whose motive they do not necessarily understand) and say "hey, you do not need to tip my wait staff." That would go over really well. Tipping or not tipping is your choice!

You decide if you want to tip or not. You can leave nothing, a few coins, a few bucks, or a hundred dollar bill. Do whatever you want. It is purely your choice. Any rationale you have to tip a certain amount is simply your rationale and your choice.

Any waitress at any restaurant in France who "demanded" a 15% tip from me would get nothing from me except a comment to the owner or manager if I knew them personally. Hard to totally blame the waitress, however, if such "demands" work more often than not.

What more clarity can there be?