Well done Aris.
My understanding is that underscore "_" are ok for html ids. (https://stackoverflow.com/questions/70579/html-valid-id-attribute-values)
We have also an example here with underscore: https://doc.tiki.org/PluginCustomSearch#Advanced_Pagination_in_Smarty_Template
So what's the conclusion of this discussion ?
Is it ok to use underscore for a customSearch id (like Tiki sample) or it is better not to use underscore (or any special character) ?