partially completely walls are for a brief moment Graphically indistinguishable from foundations. So you can’t tell if it is a foundations that your opponent can just walk through or it is a palisade with 20HP. This isn’t a huge deal, you can assume that a foundation is not started unless you have manually clicked off, unless you have short term memory problem this is unlikely to be an issue. But if you are casting a game it can sometime be hard to distinguish at a glance.
Adjusting the thresholds at which the sprinte is changed would easily fix that.
If a villager even only touches a wall foundation and starts building it : put the partially built wall sprite.