Yes, also it can be. We can't know it. But, Eat less bread, is the imperative.
He eats less bread, she eats less bread, it eats less bread, you eat less bread... (usted) come menos pan. Todas estas también pueden servir para come menos pan, pero no en todas las ocasiones.
Often, the imperative is followed by an exclamation mark.
From my reference: "Because the informal tú command (imperative) is the same conjugation form as the 3rd person singular, it is helpful to include exclamation points to indicate urgency or the name of the person you are commanding followed by a comma."
Hola hotsticks: Because in this case "come" is the Command (or Imperative) form of the verb. "Come" is the command to eat in the tú" form. "Comes" is the present indicative form also in the "tú" form which means "You are eating" or "You eat" (not a command). [reference, 501 Spanish Verbs, Fourth Edition, Page127]