In all sincerity and truth: would there be any reason why a major authentication service would deem an autograph as not genuine when in reality it actually is? Someone told me that they don’t trust even the major ones if they’re involved in selling as well. Any honest opinions? Thanks...
The major third-party authenticators don't sell autographs. Some of their staff authenticators may from time to time, but on a very small scale. The money staff authenticators make authenticating autographs is typically far beyond what they would make buying and selling. If the word got out that they were declining submissions to boost the value of theirs, their business would plummet.
There are specialist authenticators who often also sell autographs but they don't want their reputations damaged either.
Is the person who told you not to trust ones that sell, and that many or most sell, is an autograph dealer or auction house? I'm asking because that "advice" is common among those who sell a lot of forgeries.