Indeed so.
The worst one seems to be the 1897 tide mark. On many of those pennies, you can barely make out the tide at all, let alone whether it's high or low.
Agreed. I bought an UNC set of 1887 JH silver at Warwick which one or two dealers rejected as "cleaned". Well, they weren't - they had a bright 'mirror' finish, which was more pronounced in the fields than the raised designs; cleaned coins tend to show the most mirroring on the highest parts.