Generally, ECMs and their team I think should be eligible to show on the leaderboard. It shows they are experts in the community and adds to their clout.
If you are concerned about the possibly unfair advantage of points for building the community, what I've done with several clients is we turn off points during the build (massive docs adding and content seeding occurring) and at launch we award those who did all the hard work a special exclusive badge with a small points boost (say, 100 points). That way they get recognized for their contribution but aren't starting at the jump with 500+ points when everyone else just left the starting block which can be discouraging to everyone else.
I find that some people, especially champions, set their sights on the community manager (*cough, me, cough*) and see a high point level as a personal challenge. Plus, that person put in the work. I have one intern who was at the top of our leaderboard for a while because they were uploading a ton of content as part of a migration. They put in a lot of hours doing that and the points helped make the manual effort feel worth it.
I have not actually set anyone outside of the points system, although I have considered it and continue to see some merit in doing so. At this point, it hasn't seemed necessary.
All of our CMs are included in our leaderboards. We have, however, left our admin users (the user accounts we use to do sysadmin work) outside of the leaderboards.
I have had some people say that certain people have an unfair advantage due to their role in the company, but taking people out of the leaderboard would then be demotivating for that person. I think it would be difficult to come up with a system that would seem fair to everyone.