Hmm, you’re seeing some strange behavior to be sure and I’ll look into it, but I’m a bit confused about what you are trying to achieve. Make tile passable is intended for tiles that are completely impassable to be made passable. It adds edges from that tile to all adjacent tiles. If what you want to do is to create a wall between two tiles you do not need to use this function, though. Just remove the edge between the tiles like so:
This creates an “invisible wall” between two tiles, but this is perhaps not what you’re after? If you could tell me more about your intended end result I can be of more help in suggesting how you go forward. I’ll be sure to look into the 99 cost stuff. Also, thanks for telling me about the 2D stuff referenced in the main toolkit. I’ll make sure to fix that in the coming update.