Do be aware that in a certain sense, there is no such thing in RM as Webhints for FamilySearch. What actually exists is Record Hints in FamilySearch for individuals in Family Tree. Those Record Hints in Family Search for individuals in Family Tree are being used to create a useful illusion of WebHints for FamilySearch in RM.
I know that sounds confusing, but that's really the way it works. Most of the time the illusion is so good that you can't tell it's an illusion. But let's look at sort of a fake example. Suppose you have a John Doe in your database who was born in 1845 in Virginia. There might also be a one or more John Doe's in Family Tree who were born about 1845 in Virginia. There might also be one or more John Doe's in the U.S. census whose census record suggests that they were born about 1845 in Virginia.
Before RM even becomes involved in the process, a process in FamilySearch will have looked at people in Family Tree and will have looked in the U.S. census looking for matches. If it finds examples that look like matches, the process in FamilySearch will create Record Hints for the person in Family Tree. Such hints are merely proposals. They remain as proposals until a Family Tree user accepts them or rejects them from the Family Tree user interface. These Record Hints are for every FamilySearch user in the world, not just for you. If you accept one of the hints, you are accepting the hint in behalf of every FamilySearch user in the world. If you reject one of the hints, your are rejecting the hint in behalf of every FamilySearch user in the world.
When RM sends a WebHints request to FamilySearch, the request is not matched against the Record Hints that are already there. Rather, it's matched against the people in Family Tree. Again, this process results essentially in proposed matches. You will have to determine if this person in Family Tree really is the same person that's in your RM database. Whether your RM person and the person in Family Tree are the same person or not, you as an RM user will see those Record Hints reflected back to you as RM WebHints. So if the person in RM matches the person in Family Tree and if the person in the census data matches also, you should probably approve the hint. But what you are approving is the Record Hint in FamilySearch, not the WebHint in RM. Remember - the WebHint is really only an illusion.
It's actually possible that the Record Hint does match the Family Tree Person but that the Family Tree Person doesn't match your RM person. This is an awkward situation. You shouldn't reject the hint because it's valid for the world in general, but maybe you shouldn't approve it either because it's not valid for your RM database. The whole WebHints process in RM doesn't deal with this situation gracefully at all.
Actually, if you were logged in directly to FamilySearch without using RM and encountered this Record Hint, you should approve it because it's valid. But if later you were using RM for your John Doe, this same hint would show up in your RM as an approved WebHint, even though it's not really valid for your own John Doe. Another variation on the same theme is that another FamilySearch user could already have approved the Record Hint before you ever got there, and the other users's approval would be valid. The missing link in the whole process is that you have no way to approve/disapprove the match between your person in RM and a matched person in Family Tree.
Well, there kind of is a way to approve/disapprove such matches. Even before WebHints came along, RM included a very nice interface where you could match your RM people to people in Family Tree. You had total control over this process, and you still do. What's different with the WebHints and Record Hints is that RM will present Record Hints to you as WebHints even if you have not yet approved the match between your RM person and a Family Tree person. Up to a point, that's a good thing because it can help you find matches between your RM and Family Tree. Where I think the system breaks down is that there is no way to prevent WebHints being presented when there really isn't a match between your RM person and the Family Tree person who has the hint.
In my experience, this system actually works extremely well most of the time, despite this apparent hole in its logic. I take advantage of "WebHints in RM from FamilySearch" all the time. It's just that there is a hole in the logic that on rare occasions can be a bit of a mess.