Hi there,
Gaston's reply below is very helpful so I don't have too much to add apart from a couple of points.
Personally, I think I'd disavow these links a bit at a time - perhaps submit a few of them to start off with and make sure there are no negative effects, then add more over time. Right now, no one really knows how Google handles disavow because on one hand, Google say they handle things automatically, but on the other hand they still provide the tool for us to use...
1. If you don't disavow now, just make sure you keep a note of all of these kinds of links (and watch for new ones in the future) and if you do experience any penalty problems, you have a list ready to go to submit.
2. If you do disavow now, take your time to get the list right and make sure you only disavow links which are purely manipulative and / or look spammy. If you haven't seen any traffic or penalty problems, you want to be extra careful when using disavow. At the same time, if links are clearly spammy, they're unlikely to help long-term anyway, so disavowing them may not hurt at all.
I hope that helps!
Paddy
