I am, by nature, a very affectionate person and always have been; allegedly not a terribly common trait among Irish males and one that seemingly baffled my relatives throughout my childhood. (They got used to it - only took them about 20 years or so.)
I suppose it accounts, in part, for how well and how quickly I came to fit in with my Lebanese and Syrian co-religionists when I first ventured into the Melkite community - not every Irishman is comfortable being hugged and kissed three times on being introduced
(and at every meeting and parting thereafter, onto ages of ages).
Nothing has changed and I still am just as physically affectionate with my children, grandson, nieces and nephews, cousins, and their children, as well as with my closest friends and their children - and they with me. Even some co-workers see me as someone whom it's 'ok' to greet with a hug after not having seen one another for awhile (a recent consolidation of two of our work-sites brought me into contact for the first time in a couple of years with several young women who were my students for several months when they first came on-board as trainees, and I was nearly bowled over with enthused greetings accompanied by heartfelt hugs).
But, never, not once in my entire life, have I rubbed the pregnant (or otherwise) belly of any woman - heck, I don't think that I ever even did so with either of my wives during their pregnancies - and I had 5 opportunities. (Yes, I did 'feel' the kicks on request, but never randomly rubbed their bellies as some do a statue of Buddha, for luck.)
It is, decidedly, 'creepy' for a neighbor to do so and, as has been said by my brothers and sisters here, it is, at the very least, tasteless, and it demonstrates either a flagrant disregard for the personal space of another or a testing of boundaries - the one is at minimum thoughtless, the other intimidating, violative, and potentially even threatening.