In Twitter and other networking sites putting a word in between two asterisks is much in vogue.
Eg 1. Your sweet kisses, addict me. *blushes* from your warmth, spreading through my body.
2. My dear, that sex was so odious that I wish *I* had taken Rohypnol beforehand!
3. Your eyes were opened to the truth :) *hugs*
Does this kind of usage signify anything?
In the first and third examples you gave, the word in asterisks indicates an action that would occur(or you would be able to see) if you were together in person instead of communicating by text. In the second instance, the asterisks are used for emphasis in the same way you might use italics.