Recipient’s version of text is different than the sender’s version

When I type the following:

I don't think.

It looks normal on my screen.  Then I hit send and the recipient sees this:

I don¹t think.

The power of one makes me look like I don't know how to use a keyboard.

Also when I indent using the tab key, the recipient does not see an indent at the beginning of the sentence.

Thanks in advance for you help.