MIRC label doesn't bother me in the least! My only point is...if you had two used D-55s side-by-side, in pretty much the same condition, except one with an unaltered serial number, and one with the label over the serial number...and they were offered up at the same sale price...I would think most knowledgeable buyers would naturally go for the one with the unaltered serial number! This would be true on any make and model...especially on the more plentiful and popular models.
If its a rather rare guitar, then the label matters little, compared to condition, playability, tone, etc. But it should still be disclosed.
Having said that...I will say that I have owned two MIRC guitars, and they are both VERY nice playing and sounding guitars. The MIRC label does not bother me because in each case I received a substantial discount. (And both of those guitars were extremely hard to find elsewhere in decent condition.)
BTW, I never had any luck in receiving a response from MIRC as to what was done to these particular guitars. However, under very close inspection, I could see a bit of finish work that was done on both. No problem for me, and I knew going in what I was paying for.
And when I sold the Epiphone, it was with full disclosure! And if I ever sell the JF30, I will disclose the same! Because it's the right thing to do.
Interesting fact....my Epiphone didn't have the serial number factory-stamped in the headstock, so MIRC very lightly stamped "USED" on the back of the headstock. My Guild does have the serial number factory-stamped on the back of the headstock, and MIRC just over-stamped the last 3 numbers of the seiral # and did NOT stamp USED. In BOTH cases though, the label was affixed over the soundhole serial number. And even though they were years apart, they still started with the same three numbers...311.
(It's almost like selling a car with a "salvage" title at auction. Sometimes that means a car was involved in an accident that the insurance company felt it was better, $-wise, to just write off than repair. Someone could get that car and fix it up like new...and have a great car at a DEEP discount...but it still has that branded title, so re-sale will be affected accordingly. And most insurance companies will not insure a branded-title car. I used to be in the car biz and I had guys that would come around looking for salvage-title high line cars. That way I never had to turn down a trade-in.) Which is NOT to say that all salvage title cars are OK. Some are complete junk. You just have to know what you're buying. There's CarFax to help out...but we don't have a "Guitar-Fax" LOL!