Just an fyi, those stickers are illegal... Everyone uses them but they cannot *legally* void your warranty just because you open a piece of equipment you own. You might have to sue them but you will win every time. Interesting they put something with adhesive on the bottom of a CPU that by definition gets hot, I can't imagine it would stick long!
A couple of things:
First, I think you're reading a bit more into Magnuson-Moss than is actually in there. First, it only applies to a specific category - consumer products - defined as "tangible personal property which is distributed in commerce and which is normally used for personal, family, or household purposes". Despite this being "Serve the
Home", you'd have a hard time making the case that a server CPU is a consumer product under that definition. Note that many manufacturers follow M-M even for commercial (non-consumer) products, but that is at their discretion.
Next, as a used component sold by a 3rd party, it probably would not require a warranty under M-M.
Last, as a component which cannot be practically separated into sub-components (as opposed to a boxed CPU + heat sink combo from the manufacturer) none of the "tying" issues arise - one of the goals of M-M was to prevent things like an automobile dealer saying "you installed a new radio, that voids the warranty on the engine".
As far as the sticker coming off, Intel lists a TCASE of 90°C at the integrated heat spreader. A sticker on the underside, particularly with the air gap provided by the capacitors, is unlikely to experience lift.
This reference says
"The temperature range the adhesive can function in after the label has been applied and built up to its ultimate adhesion. Most pressure sensitive adhesives have a range of -65 °F to 200 °F with a paper label stock, or up to 300 °F with a film label stock."
Having said that, I find these stickers stupid and annoying as well. Either the seller has been burned in the past by people returning "defective" items that were not the actual item sold (swap-n-steal) or they were convinced by a seller of "void if removed" stickers that this was a huge risk that could go away if they just bought these inexpensive stickers. If I were selling this sort of thing, I'd make sure I had a picture of the unique markings on each CPU and which customer I sold which part to (easy when each listing has its own unique piccture).