I have Pinboard set up as a search engine shortcut in my browser, so I type "pin isogeny" in my URL bar, I get a list of papers about curve isogenies. It's pretty great.
There are probably just a couple features Pinboard would need to be a pretty useful collaborative research tool.
I have an Evernote account, which I use as a replacement for the OS X Notes app. Evernote is not especially convenient as a bookmark manager.
Pinboard is extremely inexpensive and very good at doing the one thing that it is good at and then just getting out of the way. It's fast, and it's always just hanging around as a browser bookmarklet.
If you're used to things like Evernote with a lot of fit and finish polish, you're going to be a little shocked by Pinboard. If you stick with it a couple days, though, you're probably going to end up appreciating Pinboard's design.