The most valuable thing we can do for each other is genuine commenting. Imo reposting makes no sense. Several likes from Hivers can change nothing - the Threads algo can't be so easily manipulated. But commenting can make other people join the talk or subscribe.

whether regular interactions between us will not cause suspicion sooner or later

We behave just like a group of friends... It's fine, I believe.

when we start sharing links

I think mentions of Hive on Threads are stronger than links. Let's say if we create a nice annual photography contest on Hive - like, a really good one - we can mention it now and then on Threads. Interested people we'll search on Google or ask AI about the contest.