Keep your comments as short and pointed as possible. Usually, simply yelling "left", "move', or "hey" will give the best results. For people in Australia and England, "oi" may work better than "hey". As an insult, "jerk" is easily understood, and carries better than multi-syllabic profanities. Hand gestures may compromise control, but I find that an oustretched hand, palm vertical, moving from centre to left conveys my desire to oncoming cyclists that they move to the right, and works well before yelling is a possibility.
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Je vais à vélo, donc je suis!