In this case the beauty of their feet may be a reference contrasting the exalted condition of the resurrected and glorified body where even the feet are magnificently lustrous. Thus, Isaiah's reference to the feet of the herald of Zion may be a prediction of the exalted position they are due to inherit. The watchmen proclaim the events, but now the very events are fulfilled in the people's sight. The testimony and the predictions of the prophets are finally fulfilled. This passage indicates how geographically far reaching the events surrounding the Day of the Lord will be.
Different conditions obtain, however.
This figures in well with Isaiah's more behavior based approached to identifying groups of people rather than using lineage, culture or nationality. The BofM presents a verbatim quote of the KJV in 3 Ne.