Address comment

evm/spec/mpts.tex

@@ -6,7 +6,7 @@ For each transaction we need to show that the prover knows preimages of the hash
 
 An MPT is composed of five different nodes: branch, extension, leaf, empty and digest nodes. Branch and leaf nodes might contain a payload whose format depends on the particular trie. The nodes are encoded, primarily using RLP encoding and Hex-prefix encoding (see \cite{yellowpaper} App. B and C, respectively). The resulting encoding is then hashed, following a strategy similar to that of normal Merkle trees, to generate the trie hashes.
 
-Insertion and deletion is performed in the same way as other MPT implementations, however we don't modify the MPT in memory but create a new one with the modifications. In the rest of this section we describe how the MPTs are represented in memory, how they are given as input, and how MPTs are hashed.
+Insertion and deletion is performed in the same way as other MPTs implementations. The only difference is for inserting extension nodes where we create a new node with the new data, instead of modifying the existing one. In the rest of this section we describe how the MPTs are represented in memory, how they are given as input, and how MPTs are hashed.
 
 \subsection{Internal memory format}