if you want to tinker, take them apart and add some light grease. if it turns out that they are too sluggish, take them back apart and rinse in kerosene and add heavy oil. repeat with lighter oil until you've satisfied your lust for tinkering or silence.

and yes, IME, trigger shifters make a clicking sound. possibly an intentional aural confirmation feature. remember there are people out there riding in the winter and the indexing "feel" when changing gears may be masked by gloves or mittens.