The above replies are correct. There are indeed rules and conventions regarding the use of eagle feathers worn in the bonnet to denote rank. Some are entitled to either one, two, or three eagle feathers. However, these feathers are pretty distinctive. HEre is a picture of a gathering of several clan chiefs at a Games:


The usual advice is not to wear eagle feathers (obviously), but also nothing that might be confused for one at a distance; i.e. no large, straight & tall feathers. Something small, however, like you describe, is generally acceptible and just considered ornamentation. The fellow who talked to you most likely is confused and thinks the restriction to be on any type of feather at all. It is not.