An average skilled lipreader may able to lipread up to 30-35% with a guesswork for the rest of it. Thus, missing and misunderstanding words are common. Not all deaf people are lipreaders, many of them none at all.
Read the text below which is what it feels if you were lipreading.
"HELLO HOW ARE YOU? LET ME GOT MA PEPPER AD PAN..." or another perhaps better lipreader might interpret it differently: "HELLO HOW ARE YOU? LET ME GET MY [?] AND MAN..."
Can you lipread it above and do the guesswork? Answer: "Hello how are you? Let me get my paper and pen." This is simple, but imagine an in-depth conversation and degree of speed that gets more complex. Some more possibly confusing term pairs: weather vs whether, thirteen vs thirty, and other uncountable pairs or even trios.
For us Deaf people, we prefer our natural language (e.g. ASL) in the same way hearing people vocally speak English or other languages. Next, we prefer communicating by writing/typing back and forth in English for clarity with hearing people who don't speak ASL or other signed languages. For some Deaf, lipreading is used in some circumstances (e.g. one-to-one level rather than in a group) but captioning or interpreting is preferred in educational settings and such.
Nodding away. It's not uncommon that Deaf persons may simply nod and smile to get out of the small talk. Or, simply tired of telling a hearing person to use writing/typing instead. Or, not want to drain a hearing person's patience.
In late 2007, a hearing colleague once asked me a question in our conversation. He asked, "Can you lipread?" First, out of courtesy, I replied to his question "no" and then asked him, "can you handread ASL?"
This question looks at a hierarchical hearing domination that I don't expect to fit in their world; rather we find a common ground (e.g. writing English back and forth). Perhaps better ask a question instead, "What communication method do you prefer?". If a Deaf person gestures "writing", then use a paper and pen -- don't repeatedly vocally speak which is annoying.