Standard practice is to substitute asterisk when replacing just some letters (especially vowels, and not normally the first or last letter) in a swear-word (for example - "sh*t", or "c**t").

Any random combination of other "special" characters (including but not limited to &#%!@?) may be used to denote "some unspecified swear-word".

I think OP's specific example is at least "unusual" usage. I would normally expect either "You're such an &#%!@?!", or "You're such an a***hole".

Also note that particularly with longer words such as "bollocks" (which the markup language won't let me "clean up" here), the number of asterisks may not accurately reflect the number of letters substituted. So you don't need to wonder whether my a***hole was British or American!