No harm to credit or to take out a future loan or mortgage? If you don't have to fall behind on payments, why doesn't everyone just call and request a lower rate instead of refinancing?
That's the beauty of the current situation vs the MHA days. Back then default or imminent default was required (I know two people who got denied because the banks claimed they were not at risk of imminent default. One followed my suggestion, went 90 days past due, reapplied and was approved. The other refused and stuck to his mortgage at around 8%! which he was struggling to pay, and though it only had about 10 years left on it, getting it modified to a new 40 year loan with a monthly payment of less than $1,000 would have put him in a better financial position IMHO). As a result credit took a hit, though it recovered thereafter.
In the current Covid-19 round, lenders are not supposed to make negative reports, so I had my credit score climb to over 800 while not making mortgage payments.