I noticed that when English speakers use asterisks in their comments on youtube videos or on blog posts, they use asterisks to imply actions quite often. However, I find the forms of their usage quite differing.

> 
> I knew you would do something. \* sigh \*
> 
> 
> Wait! \* Gasps \* Is that a ghost?
> 
> 
> I ran all the way here. \* Huff, huff \*
> 
> 
> 

Sometimes they capitalize the first letter within the bounding asterisks, sometimes they do not. Sometimes the verbs in the asterisks are third person singular and have -s or -es after them, and sometimes they do not. I know using the asterisks to imply an action is accepted but not grammatically correct, but at least I'd like to know their common usage. What I'm thinking is that I can put onomatopoeia or a verb between the asterisks, and that's why there's sometimes an -s and sometimes there isn't(In the examples above, sigh is a sound, not a verb, and gasp is a verb, not a sound.) Am I correct? If so, the only thing I can't figure out is why the words are sometimes capitalized and sometimes they're not. How do asterisks appear in video game or comic book dialogues? Capitalized? Not capitalized? I tried to search google, but to no avail.