This is an interesting discussion and I thought I would weigh in. I was one who totally lost faith in the BoA, BoM, the Church, and ultimately God because of issues like this, and spent ten years as an agnostic as a result. But I ultimately resolved these issues by realizing it's not important how the translations (BoM and BoA) were done, just that they were done. They may not have been perfect, nor were they weren't expected to be, but were done to the best of Joseph's ability at the time.
Once I realized God doesn't do anything for us that we can do ourselves, I began to see things in a whole new light. For instance, God could have built the ark for Noah or saved him and his family in some miraculous way, but he let Noah spend 120 years building building it himself. Why? Because Noah had the ability. He could have handed the lighted stones to the Brother of Jared or gave him the plans to build a generator, battery, and LED lighting; but he allowed him to use his intellect to figure something out. Why? Because he had the ability. God only stepped in and did that which was beyond the Brother of Jared's ability to do himself. The Brother of Jared probably came up with the worst way possible to light the barges, but it didn't matter. It was the best he could do with the knowledge he had and that's all God needs to work a miracle.
So how does this relate to translation?
When we translate something today I assume there are 5 basic steps involved: (Please correct me if my assumptions are off)
Step 1: Know the source and target languages fluently.
Step 2: Read or hear a phrase from the source language.
Step 3: Interpret the meaning.
Step 4: Figure out the best way to convey that meaning in the target language.
Step 5: Output the result.
Sometimes an exact interpretation might not be possible so they try and get as close as they can, and might even use words from other languages. Thus, "Put your shoulder to the wheel" becomes "Stick your hand out the sleeve" in Dutch.
Getting back to the pattern which God seems to have set, I strongly believe God only took care of Steps 1 - 3, and Joseph was totally responsible for steps 4 and 5. Moroni could have handed Joseph a complete printer's manuscript with perfect grammar, punctuation, and diction; but that's not the precedent that's been set. Joseph may have come up with the worst way possible to convey Mormon and Moroni's meaning in English but it didn't matter. It was the best he could do at that particular time and that's all God expected. God could work his miracle from there. It was good enough for the Holy Spirit to convert earnest seekers such as Brigham Young, Parley P. Pratt, Willard Richards, and anyone else. I firmly believe that any revisions Joseph made were done without God's input, and were only done as Joseph gained a greater understanding of the BoM and the English language. Why? Because that fits the pattern.
Did Joseph believe one character in the Egyptian alphabet translated to multiple lines of English text? Maybe. Does it matter? Not really because steps 1 - 3 were God's responsibility. Joseph was only responsible for figuring out how to convert what God gave him into English. Limited as it was it was good enough.