Basketball iMac here, using OS 10.1

plus from the keyboard is +
plus from the number pad is +
ampersand from the keyboard is &

Now to post it and see what happens:

Edit 1: came out exactly as written on the first posting
Edit 2: came out exactly as written after editing
Edit 3: came out exactly as written that time too. WoN, it must be something idiosyncratic to your system. Happy hunting :-)