Combining optical microscopy and high-resolution electron energy loss spectroscopy, we unraveled the puzzling controversy of plasmon dispersion in a Bi2Se3 topological insulator. We demonstrate that Bi2Se3 surfaces with superb flatness host dispersing plasmons. In contrast, cleaved Bi2Se3 surfaces exhibiting extensive large-scale faceting and shattering are characterized by an opposite behavior of the plasmon dispersion, i.e., the frequency does not change with the momentum. Moreover, we show that plasmonic modes are quenched in samples modified by the implantation of defects upon ion sputtering. These results indicate that the control of the morphology and the crystalline quality are mandatory in the prospect of low-loss plasmonics with topological insulators.