so as we all know blocking up claimed water tunnel is illegal, but claiming and blocking up train tunnels isnt, here is the thing, the tunnel may be placed on perfect spot and your enemies decide to strategically claim this land and block up the tunnel, blocking it up in wilderness is huge grief but its solvable issue but claming and blocking, there is nothing u can do about it. so, make it that blocking up claimed tunnels illegal aswell.
here are some arguments about this:
1) if it wont be illegal, everyone will just claim every tunnel and there wont be any train rails accesed to towns.
2) train tunnel is easy to find since 99% of them are on Y lvl 40 and everyone knows that very well, and if we make above y lvl 40, its very close to surface and if we make it above ground, it can be more easily detected, claimed, and blocked.
3) there are bunch of ways to grief tunnels already. for example spamming it with different difficult to break blocks, like heads, glass plains, leaves etc. or just blow it up ig