Putting your company 'bug' on the face of your work, very small, was a common practice among sign painters in the old days. Not everybody did it. And not everybody did it on every sign, but it was very common.
I never thought of it as a moral issue. Back in the day, I actually had customers who were disappointed when I didn't do it. "Aren't you going to sign it?" some would ask. At least some people viewed their sign as a work of art and wanted the signature of the 'artist' on it. And I don't know how many times I got calls from people who said they got my name off a sign I did.
I didn't put it on the face of every sign, but I usually did. Sometimes on a post. Always a label on the side of a lighted cabinet. Always tiny and inconspicuous. You had to walk up to the sign to read it.
During my Arkansas years, I was the only shop that consistently put my name on my work. There were two other shops in the county, but people often told me they thought I did all the sign work. I even got credit for signs I didn't do because my name was on so many of them.
In the 42 years I've been in the industry, I recall only a few times a client asked me to remove my logo. Once, I had put it on dozens of sandblasted redwood signs that I did for a bunch of different apartment complexes all owned by a huge Chicago real estate company. It was small and centered in bottom border—sandblasted. The buyer called me and said that the company owners wanted to know how difficult it would be to remove the logo. I said it would be very difficult. He said, "Nevermind, then. But we prefer it not to be there in the future."
As a cub I worked for a shop called SuperSigns. They always used a little five-sided gem shape for the dash in the phone number, instead of the dash. In the middle of the gem was an SS, similar to the S in the Superman comic logo. It was low contrast, but always there. Once, years later, I was trying to talk a store owner into re-doing his sign and he took me out and pointed to the little SS on the sign. He said, "I'm not ready for a new sign yet, but when I am, I will only have them do it." It was a status symbol for him.
But, I know times have changed.
Brad in Kansas City