You have got to be kidding me. I have given you this information several times already (including in each and every approved appeal for one of these trail markers AND including in the topic I made here when two of these trail markers were removed back in October: Restoration request for two hiking trail markers that were inexplicably removed which you yourself restored, I might add!)
But I guess if you want to see it again, I’ll explain it to you again.
These stickers are not “selfmade”. They are part of an official network of hiking routes throughout the province of Noord-Brabant that is created and maintained by the province’s tourism organization (www.visitbrabant.com). You can find more information about the hiking routes specifically at https://www.visitbrabant.com/en/experience-north-brabant/unique-routes/walking.
As seen in the above image, the symbol they use to map out their hiking routes is a green square with a yellow triangle that points towards the direction you need to go in to follow the route. In wooded areas, they will use wooden posts with plastic signs, but in urban areas, they make use of stickers instead, since it’s easier to just stick those on street lights, traffic lights and other already-existing infrastructure than to put up wooden posts everywhere.
And these stickers are about as permanent as it gets, since they have an entire section of their website dedicated to maintenance: https://www.visitbrabant.com/nl/routes-in-brabant/meldpunt
If any of the stickers are ever damaged, illegible or outright missing, people can file a report on that page and they will send a maintenance person to fix the issue ASAP. And this system cannot be abused to get them to place stickers where they shouldn’t be, since they have their routes thoroughly mapped out here: https://routeplanner.visitbrabant.com/nl/wandelen and they are not going to place markers in the wrong spots. This in fact makes it very easy to check for abuse of any “selfmade” markers: if it’s along any of the routes on that map, they’re official. If they’re not along any of the routes on that map, they’re fake. The locations of all of the markers I mentioned in the original post can be verified to be along the official routes using the map. There is zero abuse going on here.
I would love to see whatever information you have that led you to reach your conclusion.