Welcome eb! Not to worry. When in center city remember that there are cameras all over the place. If you are in the Old City section of town I doubt very much you will have any issues. However if you act like you are doing something intrusive people will get upset. Use common sense and don't shoot private property. If you shoot say Elfreths Alley, people expect you to be shooting there. I know that when I was shooting at the end of Market Street in Old City the people at the bars and in the cafe's were actually asking me to shoot them. On the other hand only a block away a homeless person was cursing me and threatening me about taking any pictures. Be aware of the expresions of others, don't shoot private property, and use god old common sense and you will be fine. The bridge thing was a fluke and I wouldn't be too concerned.