Hitsounds from notes and sliders must be audible. These provide feedback for the player, and having them silent in a rhythm game doesn't make much sense. If you don't like the default sounds, then find replacements rather than silencing notes. You can use hitsounds from the Custom Hitsound Library or easily find others online. Lowering the volume of a few notes to provide a dampened effect is usually fine, but complete silence is always unacceptable. The end of a spinner (or even the entire spinner) the sliding sound of a slider, and the end of a slider can be silent, but only do it if it makes sense. Finally, you cannot silence both slider ticks and slider slides together.This is what the rule currently says. However, it's not very clear. Silenced samples are not allowed unless used with other hitsounds, but it's allowed to silence notes using green lines under certain circumstances, and the rule worded that way doesn't effectively describe that.
The first part is quite useless. It's obvious that hitsounds must be audible. If you're adding a circle and muting it, you should just remove it - the fact you're muting it proves that it doesn't fit. This is common sense. I propose this:
You cannot use empty or silent samples if they are used by themselves except for sliderslides, sliderticks, and spinner sounds. Using silent samples for sliderslide or slidertick is allowed, but not both at the same time. Additionally, hitsounds from circles and slider heads must be audible (this is measured using the default skinsounds and settings). Silencing the end of spinners or sliders is allowed if done via inherited sections.This is I think clearer. It allows for occasional silence of both sliderslide and slidertick if needed, but still keeps the previous rule as it was meant to be.