If after thinking about this you don't think any formal acknowledgment is called for, that's legit. The honorable thing is not to send a card or whatever because a critical mass of voices here agreed on that, it's to do what is right for you. Which may be nothing.
Adinva 51, S20, S18 M24 total 6/15/11-12/1/12 From IDLY to H moving out 9/15/15-3/7/17 From negotiating SA to final D at age 50 5/8/17-now: New relationship with an old friend __ Happiness is a warm puppy.