Never Let Anyone Sign Your Covers!

I am looking at a photograph in the Private Treaty section of an upcoming Bolaffi sale. It shows an 1858 cover with a bisected Romagna stamp catalogued at a cool quarter of a million euros. The bisected stamp is surrounded by SIX pencilled autographs and one handstamped signature. Bottom right of the cover there is a further pencilled autograph. The catalogue lists them all: Giulio Bolaffi, A.G.Bolaffi, Emilio, Alberto and Enzo Diena, Mauritio Raybaudi and Renato Mondolfo.

I am asking myself, By how much do these signatures and the handstamp reduce the value of this item?

Consider:

(1) If you try to rub out these signatures, you not only cause surface scuffing but risk creasing the item - something all dealers have done (and often do) when they rub out one pencilled price to replace it with their own

(2) You can't rub out a handstamp. If someone makes a mistake with a handstamp, it has to be crossed through in ink and a correcting note added - I have seen this often enough on the backs of stamps. Who wants a stamp or a cover which is a visible record of someone's mistakes?

(3) It can never be clear what a signature is signing. It is always ambiguous. That is why a Certficate is necessary to clarify what has been signed. But if you have the Certificate with a photograph attached, you do not need the pencilled signature or the handstamp: it's redundant

(4) A cover can be altered after it has been signed - something added or taken away to "improve" it. In that sense, the signature is strictly worthless and potentially misleading. In contrast, it's a lot more difficult to amend a Certificate. Of course, you can fake it outright - but that is generally a lot more difficult than forging a signature or even faking a less valuable (but signed) into a more valuable (but still signed) cover

(5) The cover is supposed to be a collectible object and to be preserved in the best state possible. Signatures deface the object. No one would hand the Mona Lisa over to a bunch of experts and invite them to decorate it (in felt tip?) with their signatures to "prove" its authenticity.

Conclusion? I reckon a cover decorated with signatures is worth about a quarter to a half less than a cover without them - and as part of an Exhibit, it ought to lose points in a similar proportion.

Am I wrong?