Both of our Bockmann trailers have or had plastic clear partitions and have not caused any problems, as stated above the horse doesn't lean on them, only brushes against them on entry/exit. They are also easy to clean
My Henra trailer had one and it was great. It made the trailer interior a lot lighter, not dark and gloomy for when the horses walked in. It was a heavy plastic and hung as well as a rubber one. The steel bar it hung from was round so no edges. I wish that I had one in my current trailer, an older Cheval Liberte.