Thank you all for your responses.
Bill, never even considered measuring the TDS on shore water. Lesson learned, especially if staying at same place more than one tankful or so.
Barry and Robyn, yes, the anode we installed on 4/14 when we left for Nova Scotia was 100% gone by 11/16, so it lasted less than 30 months (no inspections in between). The anode we installed on 11/16 was I would say 25% gone by now, though after I took the picture, cleaning the heating unit, I accidentally broke off the top 40% of it, so perhaps it had weakened internally beyond the 25% apparent wear. Anodes are €12 and DHL will not transport them, so buy local. Quick recommends annual inspection.
Bill_9895, yes, people on internet recommend setting the thermostat to a mere 120F (50C) in hard water places to avoid scale! For now I will set at 60C as we'll be in warm areas for a while. I was just stunned because on previous inspections (4/14 and 11/16) there was either no scale or vanishingly little.
SM2K Nr. 350 (2002)
At anchor, Bozburun