Hi!
I have left the brackets there intentionally, as I thought they might be dangerous yet. It turns out they are not. I’ve made a tiny modification on the plugin code on your server, so the “(” and “)” characters are not removed when indexing. Also, I’ve re-generated the index table, so it should return result for C18DSL(H4) now.
I will investigate more of these special characters for the upcoming version, so I can enable more.