If warranty departments really give hassles because a knife has been adjusted, opened, or deep cleaned.....that's just insane. I hope that is not really the case, and just that of internet B.S.ery. The finish production line are just people too, and I have received many knives (even many high priced ones), that have had too little or too much tension on a screw or pivot. In fact, I have probably had more higher end pivots that were too tight, and lock-tited in place, than those that were just right. Adjustments are VERY commonly needed on just about every brand I've purchased.
I've only sent one knife in for warranty work (disclaimer: not Spyderco). In my eyes, it was clearly a warranty issue, and more importantly a safety issue. And it was received by the company, receipt acknowledged by multiple people according to the included form, then promptly returned to me with absolutely nothing done to the knife. No notes (even cryptic ones), no reasons why work couldn't or shouldn't have been completed. This particular over $300 knife was like new, looked new, and could have been fixed by a trained smith in under 10 minutes....maybe under 5. Instead, I did the work myself, which took well over 2 hours because I did not have the tools, knowledge or confidence in something I'd never done before. So I took it very slow, assembled, tested, disassembled, tweaked a bit more, assembled, tested, disassembled......until right.
According to some, even the act of adjusting the pivot to function properly will void warranty. And especially disassemble and cleaning would be a problem. I would hope that manufacturers know that they are not ONLY selling "safe queens". Some of the knives in the world actually get used, and may require deep cleaning to avoid prematurely wearing out parts. There's nothing like a few grits of sand embedding themselves into a ball bearing race.
All that being said, the above was really just for those that are afraid to do ANYTHING because of warranty. But, if a knife is not finished to the level of quality required or even expected, I would be the first to send back to the dealer. But for small issues and adjustments, I would just do it myself.
I've already mentioned this in detail on other threads. But just got in a new Spyder Positron. Fit and Finish was very well done. But there were a few parts of the design that made it less than optimal. So from adjustment of the pivot down to grinding at the CF with dremel and buffing wheel, I made it my own. And in my eye's, actually improved the form and function of the knife. Even though I've slightly changed the shape of the CF, if something odd happened to the blade (which I haven't touched "yet"), I would fully expect the manufacturer to participate in it's correction.