According to Mr John Gray, it's "common" to have a settee outdoors. Maybe it's not so common if you are in Australia rather than Wales? or maybe it's more common when you call the settee a couch or sofa?
Harry doesn't seem to mind being common, he has claimed the couch on the deck as his own. Of course Harry probably has an identity issue given that greyhound racing is the dirtiest, commonest sport around but greys are historically regarded as aristocratic and elegant. In some places they could only be owned by nobility.
I had a look for a list of characteristics that make a person "common" and it would seem that the qualifiers are as many as there are people:
- large tattoos
- drinking light beer
- eating wonder bread
- having a trampoline that covers more than half the backyard
- outdoor settees
- broken down cars on the street
- teen pregnancy
- baby bumps on display
- fake tan
- regional accents
- eating in the street
- arguing in public