I'm asking myself who is vandal here...

One is fantasy other is reality, unfortunately you seem to live in first one. I don't mean anything against you but I see you are really keen to support your patriotic thinking and doing whatever to destroy what you think is not right in your opinion.

I'm just trying to keep map in accordance to reality rather than fantasy.

It's sorry to hear that you promote violence so heavily.

Myself I prefer to stick to non-aggression principle

You haven't been there apparently unlike some of us who spent many days there, also mapping all the roads that were not previously on the map. Also mapping surrounding areas to make map more useful for tourists.

Really sad to hear such hatred towards peacefully minded project.

If you really want to see what is happening there I recommend you to sit in a car and drive there.

I would say it was Croatian vandalism and building or ruins of building still exists. It has existed before Liberland creation. So don't just remove things willie nillie without going there and knowing real situation. People still live there, even if police destroyed buildings and stole private property. Also I don't see a point of removing street names. They were named by people living there and therefore have local reference. They haven't had names before and are still refered by the names you have removed. Let's not be political here but show real situation on the ground. And if you son't live there and don't know situation you can't know what's really happening there.

According to link you have provided on that plot of land there is Liberty street 1

Ok. Just try to keep the map as true to nature as possible. So don't mark buildings, if they are not already standing in reality. But residential area I guess is good enough category.

Hi 2 Liberty St. Are you settler there?

What is the point of having Liberland Marina 1 and Marina 2? To my knowledge only marina you have marked as "2" exists

Hm, well it certainly has special status, as people going there are treated differently than going anywhere else. We know this is area of Liberland but we also know Liberland still isn't recognised from any UN country yet. It isn't in Croatian cadastral maps neither it is on Serbian ones...
Well there is wiki where we could discuss this:
osm.wiki/WikiProject_Liberland

I think we should discuss how to prevent vandalism, but at same time allow naming of places that people are now building and living on. Many people want to add fictitious locations on that map that doesn't exist in the nature. But at same time there are buildings being built there as I'm writing this and if places exists in real life then I think OSM should also reflect that. But I guess it depends who will be reviewing this area. Someone who is against what's currently happening there will most likely delete all. And someone who is overenthusiastic will add points all over the area that well don't really exist. Same problem is with this area on Google maps. I don't know, but this area will most likely face many changes in the future, so I don't know how OSM will handle this dilemma.

How then to properly mark this boundaries?

Well I think to be fair to all OSM should have option to add disputed areas and show claims of different countries. This would be also useful for travelers so they know they could get in trouble just by moveing in certain area that is disputed.