If one keeps reasonable vis, rain hasn't been an issue for me. I prefer brown polarized sun-glasses when I'm in the rain, they seem to improve vis, or discernment, at least.
Flying through rain can peel blade paint, although it's more likely to tear up blade tape.
The carb heat suggestion is also a good one, and/or engine inlet anti ice.
I've used various polishes for years, Brillianize and Plexor work well. Frankly, I figure keeping the bubble clear is worth the chance that it *may* be an issue if it has to be removed and resealed. Penny wise and pound foolish to sacrifice vis.
Yep, encountered the misted over bubble, airflow's the only thing if you don't have really good demisting, or better yet air-conditioning.
Final thought, even with a polished bubble, be prepared for a significant degradation of vis if you shoot an approach in rain. The water stops blowing clear, and gravity takes over, works more gently, and water accumulates blocking your view just as things get interesting. Wipers, big side windows, or doors off help.