Hmm! That is exactly what one of the links stated, I believe the Second link.
If you don't want to click on the link, here is a quote from Apple:
Emoji sent to non-iOS devices may not render correctly, because the receiving client must properly translate and display emoji.
When using emoji in messages, mail, or other text fields, you may occasionally encounter the following:
- Emoji may not display as expected or match the sent emoji.
- Instead of emoji, the other device may display squares, equal signs, or question marks.
- Unexpected line breaks may appear before or after the emoji.
- You may be unable to reply to email messages that contain emoji or other unexpected characters. You may need to remove these to reply to the email.
- Emoji may display correctly when using iMessage, but not when sending to another carrier using SMS or MMS. See this article for more information.
If any of the above issues occur, try to resend without using emoji"