Is there an equivalent to speech impediments, like if a signer’s fingers can’t move a certain way?

Answer 1

Absolutely. I have experience with people who are missing fingers, have advanced osteoarthritis, have tubes/wires/etc. in hospital beds, have no effective use of facial expressions for emphasis due to paralyzation (stroke, CP, etc.) and all of those things make a sort of "impediment" to clear understanding. Similar to a hearing/vocalizing person, anyone who is skilled in communication can work through that and still understand the person. People also tend to get used to it and sign even more clearly or people around them learn to read their more subtle movements and see past that "impediment."