Other registrars allow me to accept Sedo or Afternic with a click through e-mai
In my opinion, that's precisely the advantage of Dynadot. You can make a wrong click on that email, and you have already accepted for Fast Transfer your domain for someone else.
In Dynadot, you have to enter into you account and click to accept your domain to be listed at Afternic (and you can select them and accept them in bulk, if you want). And also, you will be able to see in your control panel, which domains are already accepted in Afternic, which are "pending" for acceptance in Afternic, and which are not. This doesn't happen at Godaddy, for example.
Also, at Dynadot you can remove any domain from Afternic when you want.
This doesn't happen neither at Godaddy, where once you accept a domain at Afternic, you cannot see its Afternic status, if it's listed or not, nor you cannot remove it later from Afternic.
And at Dynadot you can make a lot changes in bulk, selecting between a lot of options. It offers a lot of features and flexibility for people managing their domains.