If more than two guitars is playing in a session, it makes sense for one of them to be capoed up high and playing different chords, so they don't get into each other's way. Two, four, fiive, seven frets up, whatever suits.

All right, you can do it other ways - for example, you can leave off the capo and play different inversions, if you're up to it. But using a capo is a simple and straightforward way of opening things up when someone else joins in with a guitar.

Using a capo needn't be about being unable to play the chords without it. It's about getting a particular sounds with particular fingerings. It's about being grown up and not posturing about being a clever boy (or girl).