This may mess up especially interprocess communication, a notoriously problematic field. A not so improbable scenario would be the addition of encryption to enhance security. The channel system invokes the blockcipher to encrypt the line, but not all characters are encrypted due to the length of the line not being a multiple of the blocksize. Especially the EOL-character is neither encrypted, nor transmitted. The receiver decrypts the blocks it got, then waits for the EOL character.
Data compression is another good candidate for such a situation.
Because of this I decided to include the number of characters buffered by a certain transformation in its description.