What steps will reproduce the problem?
1. Create a character with a short name i.e "He", or add "He" to your highlight list
2. Have someone say a word with He in it i.e "Healer" if your character's name is "He"

What is the expected output? What do you see instead?
input -> desired output : current output
Healer -> "Healer" : ">He<aler"
He -> ">He<" : Same
He. -> ">He<." : Same
aHe -> "aHe" : "a>He<"
What version of the product are you using?
r221

Do you have an error log of what happened?
This does not produce an error, but annoying results, and makes the name highlighting feature unusable.

Please provide any additional information below.
I do not know much of how Chatter checks for highlights, but if its regex you could use word boundaries (\b).
Sorry if its unclear, I'm not sure how I should explain it, but basically the highlights don't check for boundaries, causing words with your highlight in them (without the word being your highlight) to highlight.