We don't get a mail notification when an entry is moved to an other activity in a community.
USER A does the following:
1) Create community
1b) Add User B as member in Community
2) Follow Community
3) Create Activity AAA in the community
4) Follow Activity AAA
5) Create Activity BBB in the community
6) Follow Activity BBB
1) Creates Entry1 in Activity AAA
2) User A gets a email that the entry is created.
1) Edits the content of the Entry 1, so User A is last modifier of Entry1
1) Moves Entry1 to Activity BBB
2) User A does not get an email that Entry is moved to Activity BBB
Unless User B selects to manually notify other people about the moved activity entry, the other activity members will be unaware of this change.