Is this appropriate or is it Facebook stalking?

[bingoelissa33]

An ex-boyfriend from high school that has been a friend for years got engaged 2 months ago. Is it appropriate to comment on his Facebook page congratulating him?

How long after an event, like someone getting engaged or having a baby, can you comment on their page?

We aren't super close anymore though. So it leads to the questions, "Why are you looking at my page?" I guess you could say I was clicking through their page. I feel weird because that's like "Facebook stalking" even though we are friends. It happened too long ago to be on my News Feed.
Oh no I definitely don't have feelings anymore. We dating when we were 14 over 10 years ago. I guess I Facebook stalk everyone of my friends. I'm not very good at being social. I never post anything on Facebook, I just click around on it and look at my News Feed.