Real simple to reproduce. Change the default font size (14 for example). Type your message and add a smilie. Continue to type your message and post.
Example
Hello world how are you? 
Another example here
smilie render
I have just uploaded a fix which should ensure that smilies get a padding to nearby elements, preserving a proper server-side detection. Since this changes the way the editor handles the converted BBCode output, it will not affect existing posts.
Don’t have an account yet? Register yourself now and be a part of our community!
Well whatever I did there. I also did on my site too.