A比B+adj.+多了means "more than"。ex,你比我高多了you are very taller than me. A比B+多+多了。 the frist 多 is adj. means many or much, and the second 多了 is adv. express a high degree. so,你比我吃得多多了，你比我写得多多了，你比我穿得多多了 all are right. and i have a question for u , and you think it by yourself, haha 你比我吃得多 and 你比我吃得多多了 these two sentences means are same??

Oh you expressions above are orrect. Chinese is free structive language. Sometimes there are many different kinds of orders to,express one meaning.

What Brian said, or you can simply drop the 多了 (thus eliminating the 'many') 他写的字比我写的多。 or you can tack on some other phrases to describe it 他写的字比我写的多得多 他写的字比我写的多得不得了 (duo1 de bu4 de2 liao3 in case you haven't learned this structure.) (This like saying "an awful lot more")

You can definitely say 多多了, which means "many more." 他写的字比我写的多多了 --> he wrote many more letters than I did.

有时候我们也会觉得两个多字叠在一起好像累赘或饶舌，也可以换一种说法：“多得多”：他写的字比我多得多。（顺便纠正前面的错误：“写得字”应该是“写的字”）