I spent 16 years flying aeroplanes that surged merrily- VC10 and B747-100 (Pratt & Whitneys) and to a lesser extent, B747-200s. Surging caused no ongoing problems. I believe they are no more serious than a backfiring car- indeed usually if the engine parameters recover themselves, you can leave the engine running normally. A surge with no reasonable cause, like power change, is often a 'don't use', 'no relight unless really needed' restriction. As long as they don't bang for too long they are harmless. The cause is incorrect pressure distribution through the engine, usually just pressure relief valves not spring loading open to relieve excess pressure, so the air finds a new way to go!