True, but on the other hand, with a truly orphaned work, the odds that you will ever need to defend it in court are very low.
Again, the cases I'm discussing, the works were clearly abandoned, as users had been posting the works for years, while readers kept searching for any clue as to who owns it so they CAN pay them. Clearly, if the owner was still around, they'd have objected or filed charges years ago. Somehow, I doubt they're suddenly going to pick the one individual with the least ability to pay, or even that there's anyone who even knew the original author created the piece (otherwise some distant relative or ex-wife would file a claim as his last-remaining relative).
Thus, the risks are essentially nil, regardless of the potential worst-case costs (just consider how many family members know an SOL author is writing online porn).
Again, I was outlining the currently accepted procedure on handling unknown, abandoned copyrights, rather than how to guarantee you'll NEVER EVER be sued by anyone in your entire life.
The short answer, do you due-diligence, demonstrate you made every effort to find the original creator, mention in your work that you tried to find him for proper approval but were unable to (with the implied assumption you'll yank the work if the rightful owner objects).
Legally, there's little a court would ever object to with such diligence. The author, in that case, did everything right, other than conducting a seance. At worst, the case would be extremely short, with the judge deciding 'either remove the usage or pay the agreed upon fee'. In short, there's NO malicious theft of someone else's work. So unless the original creator has been in a comma for the past decade, and woke up with a instant desire to sue anyone he can find, the odds of a suit of any kind are ridiculous.
Beyond that, even if they DID sue, there's little they COULD claim. Not only would they have to ask for monetary damages based upon your earnings, they'd then have to determine what influence a single font on the cover had for the limited profits you earned.
True, there ARE penalties if they ever filed an official copyright (something few individuals file for), but they aren't as likely to initiate a lawsuit when facing financial losses (lawsuits AREN'T cheap for either party, so they're unlikely to sue anyone without the means to pay for the lawsuit itself).
Once again, I find your complaints spurious. I'm not saying that you don't have a point (about your legal risk), I just think you're taking the my arguments out of context (as is your want).