Trello suspend notifications to all members

You could get this behavior right now by creating an organization and inviting everyone you want to be able to vote and comment to the organization, then creating a board within the organization and making your internal users the members of the board. Then go to board preferences and make the board visibile, votable, and commentable to organization members. It's a slight abuse of organizations, but it'll get you the behavior you want.

The side effect, right now, will be that the organization's existence, and its memberships, will be public-visible. Private orgs are in test right now (https://trello.com/card/board/private-organization-profile-option/4d5ea62fd76aa1136000000c/4e7206a8ec4fdc00003e63e7) so if the organization needs to be completely invisible to the public, you would want to wait for that.

The way I found to do this, is by changing the Board permissions so that only members can make changes to the Board. People in the Organization can view the board, but they can't become members unless invited to the board.

This way I can invite people to the Organization, let them view the board, and still, they will not be authorized to change anything on the board, and can't join the board without my specific action.