If the star is visible with the naked eye, then it will already have an accepted name and no certificate will change that. Why not just pick a star in the sky (Sirius say) and resolve to think of the loved one whenever Sirius is sighted.
I realise people may get comfort from having a certificate saying that a particular star has a loved ones name and if this is done without money changing hands, then it is harmless. However, this is just my point. In many cases it is not free. Sydney Observatory charges $300. Money is extracted from people suffering bereavment under the impression that the name has some official recognition. If there was some qualifying statement on the back of the certificate such as "This star name is only recognised by our list. Other people on other lists may also have paid to name this star" then I might find it more acceptable.
Geoff
Note added:
This site is at least honest. They say
"The scientific community refers to stars by catalog numbers and astronomical coordinates. Your star name and message will be recorded in our database and in an orbiting SSI Archive, but no star-naming service changes the scientific designations of stars."
If they all did this it would at least be clear to people who read the fine print.