Just out of curiosity, is building a reactor the only way a player get's the station marker for M7 or would they get it by building a Trident?

You dont get it by building a trident, only a reactor

what if one has not yet built a reactor but destroys a ship carrying one and takes it, would one then be able to dock at M7? and what about the waypoint?

If you can find the station and the docks, anyone can dock. It's easy to mistake a dock for an exit though if you don't have the marker.

Only actually building the reactor will get you the marker, currently. As Fluffy says, however, it is a convenience, but is not actually essential. Especially if you have a friend who does have the marker, since they can lead you in. Otherwise, trial and error.

It should be an easy enough change to make it so that either building the reactor or building a trident make the marker visible (would just have to give the appropriate accomplishment at the end of the build trident mission). There's no reason for someone who builds a trident without having built the reactor to not have the marker visible.

Of course, that change wouldn't do anything for people who have already built the trident.

To call the marker a mere convenience is a bit of an exaggeration. I can find the M7 station entrance in about 20 minutes while flying a moth (without the marker), but in a trident I imagine it would probably be more like an hour at best. Tridents are so slow and the station is enormous. And seeing how that is the only station where tridents can dock, that is simply poor design to not have the marker visible to all trident pilots.

I definitely agree.

In my opinion, there should be a second component that gives the marker when built. One of the harder ones.