A star shaped symbol (*) used to correct
or clarify a spelling mistake when said mistake cannot be edited. Typically you'll see these types of corrections in chat rooms, text messages, or fast comment chains. These corrections can be applied by the original commenter or by another person.
(Asterisks when commenting on a cat picture on Facebook)
Jess L.: If you kep putting that cat in sweaters, your going to get mauled.
Jess L.: keep*, you're*