As someone who spent embarrassingly long trying to log in to a system one afternoon because I was misreading an "l" as an "I", I can say that it does sometimes

As someone who spent embarrassingly long trying to log in to a system one afternoon because I was misreading an "l" as an "I", I can say that it does sometimes matter - it doesn't need to be in the same word. Then again, since you set the challenge - lamb and Iamb I can see no good reason for us to ever use the same symbol to represent two different letters, that's just silly business. Edit: for the record, I didn't downvote you. Interestingly enough, I just noticed that it looks as though I can no longer downvote direct replies to my comments. Seems like a reasonable rule to have in place.