Someone had mentioned in another thread that a dirk ruined an otherwise good casual kilt ensemble that he had seen. From the description of the outfit (traditional kilt with button-down shirt, etc) I agree the dirk would be a little out of place.
However, I don't know when a dirk would be considered appropriate- formal wear? For specific occasions? I'm just not familiar with the conventions of wearing a dirk with a kilt. Any insight or opinions would be much appreciated.