It's usually pretty discreet - they'll stay out of your line of sight and, if they're doing it right, you should barely notice them stepping in to top up your wine, etc.
Not sure what star rating system you're going by (Michelin only goes up to 3), but I'd expect that level of service even at 1* restaurants.
I'm meaning hotel (and therefore the bars/other within them) ratings rather than restaurant stars.
Maybe years living in a somewhat ropey town and having to be careful in alley-ways and tree covered areas has tuned me to be extra sensitive to people trying to stay out of line of sight…