every time i see the word Unix this U is *'ed or some other letter in the word is stared is it bad luck to say Unix or something?

Most people do that to prevent the "trademark" symbols, perhaps to avoid copyright laws. (Various countries have different laws - using the name is not a good idea in some countries.) Another reason is the same reason that so many people use various words related to MicroSoft (tm)...

Isn't the * symbol for wildcard, so *nix means anything Unix based which is easier than saying "Linux and Unix" every time.

Jabird: they're both right.

Maillion is right because at one time AT&T vigorously defended
its Unix and related trademarks. Hashing up the name was a way
to make the reference but without having to add the (tm) symbol
and "Unix(tm) is a trademark of AT&T" footnote.

Tokes is right because collectively referring to all the various
flavors of 'nix' with a wildcard is simple and efficient.

Xenix
AIX
HP/UX
IRIX
Linux
System V Unix
BSD Unix
.
.
.
and so on.