In case you're like me and you kept trying to plant/defuse using the F key because of other games. Everybody I play with thought you couldn't double bind at all, so I hope this is useful.
We left a lot of latitude for double binds, but can't guarantee it'll work the way you want all the time.
For example, with double binding Use and Use Spike: if you have a Cypher camera dart in you and you try to defuse it'll try to remove the dart first. That's just one of the cases where it's hard to guess at your intent because different tactical situations call for different priorities.
For people who want 100% predictability, keep the binds separate. If you can roll with the quirks, double bind your hearts out.