If I set a BSP block to "Passable" it still behaves as a solid object when using c_move even when IGNORE_PASSABLE is set.

Besides setting the block to Passable, and setting IGNORE_PASSABLE in c_move, is there some other step I am missing?

I've tried this in several projects and it behaves the same in each.

I just tested it and Im getting the same behavior

Maybe you can compile it as a map entity, import that entity in your target level, then set that map entity as passable, and then its treated as an object which should work with passable.

I found some info in the manual, maybe theres a workaround here:

Passable:
Obsolete flag, for non-mesh levels only. Makes the block penetrable and its surfaces visible from the inside.

Invisible:
Invisible block. When setting the Invisible = None flag in the map compiler dialog, the block is still used in the BSP tree, can clip away objects behind it, and throws static shadows. Otherwise it's completely invisible for the view and the AABB collision detection.

Detail:
Detail blocks don't affect the BSP tree, as normal blocks do. They can be used for small details in the level, like small pillars, ornaments, rounded arcs or other elements which would otherwise increase the portal count and building time. Because Detail Blocks do not suppress the rendering of the scene behind them, they should not be used for objects that hide much of the level - otherwise they will reduce the frame rate. Do not try using Detail Blocks as level boundaries, and don't let them touch or intersect other blocks. They are ignored by the collision detection.

I appreciate that. I did not notice that it was considered obsolete.
I see, if I do not compile the level as a mesh, then it should work. I probably won't do that, but it makes sense.

Thanks!