One of the more eyebrow-raising and sideways-glance-inducing practices is to wear a tie bearing the colours and insignia of a school or regiment to which one has no connection.
Regimental ties may not cause quite as much fuss, for two reasons: First, they are commonly inherited and kept as family heirlooms, thus the connection, though not first-hand, is strong. Second, regiments don’t typically have the problem of associated gift shops popping up all over the place and diluting the strength of their stripes.
It is one of the uglier afflictions that beset my hometown of Oxford, and many other university towns like it (though there is no place quite like Oxford). The effect is not just a dilution, but a dual dilution of both the salience of the ties and of the keenness of those with legitimate association to actually wear them.
Nevertheless, many of these ties are simply masterpieces of sartorial design, and therefore, I venture, may be indulged in occasionally on purely aesthetic grounds. I.e., the wearer should indulge in the aesthetic, not the association. Such a modus operandi has the benefit of being far less likely to foment friction and bad feeling in the event of an interview with a genuine old boy.