This information is from the Blizzard EULA/TOS, so would have been included with WoW's initial release. (For all I know, this might even extend back to the beta release, not just the public release of the game.)
I'm told it can be clearly argued that the WoW patches are not allowed per the EULA. However, those same terms of the EULA that say no addons/modifications can happen would also preent other popular addons, such as Cosmos. However, Blizzard clearly allows modifications. In their release notes to players about new versions, Blizzard will even document the changes made to their APIs so that developers can make addons, and the game has an "Addons" button on the character select screen so that addons can be enabled and disabled through the use of some checkmark UI elements. Clearly if such addon modifications were something Blizzard didn't want people to be able to use, they wouldn't be supporting their usage like they have been.
Some very popular features that have appeared first in third party addon packages, including additional action bars, visible times under buff timers, and a more advanced quest log, were made obsolete (or at least less important) due to Blizzard's inclusion of the features in newer versions of the game (without any third party addons being needed). At the time of this writing, I haven't heard of any official word from Blizzard regarding if and when they plan to do that with the nudity-enabling Patchin' Batch.
This information came from an E-Mail dated July 30, 2005.
Techlead's comments were linked to from an August 28th, 2005 Allakhazam post.
In all fairness, although the above information suggests the nude patch would be allowed, there is more information on the topic.
A post on Allakhazam has pointed to Blizzard of Europe's postTechlead's input on this topic. (I haven't found a copy of the text since the forum post has disappeared from the old URL, but basically Techlead's commentary was not in support of using the nude patch. I believe he was even apologizing, as a representative of Blizzard, for any incorrect information that a GM, who would be a Blizzard employee, might have said.) Techlead works for Blizzard of Europe, and it's been said (somewhere) by (some WoW-playing customer, presumably) that CM's (which I later learned is a "content manager" for the forums) outweigh statements said from a GM (Game Master, one who interact with the game and can make changes).
I believe a useful way of looking at this is to see a comment made about Microsoft. Microsoft's DirectX capturing abilities was replacing Video for Windows, likely in an effort to get consumers to use newer DirectX technology. Then another group within Microsoft, likely responding to some requests by businesses, released Video for Windows DirectShow filters. This kind of repaired what was broken, and probably intentionally broken in the newer software in order to kill off the older software. Conflicting efforts can be explained by a comment (I believe on a post on VirtualDub's forums) that stated that Microsoft is made up of numerous teams of people who don't always see things in the same way, or pursue all of the exact same detailed goals 100% of the time. I suspect this may be Blizzard's position: There isn't a clear official position, and so some different details have been released by different well-meaning employees of Blizzard. These statements seem to be conflicting a bit, and likely will until the issue becomes a big enough topic that the company decides to make a more official stance that will be followed more by employees. (Hopefully that won't need to happen.)
As for whether to follow TechLead's statements or someone else's: I'm planning to follow the information given on the web page suggesting it is okay. Not only was that said directly to me, but it comes from a Senior or Lead GM, according to the following paragraph: "
It is important to follow these guidelines in the immediate situation when dealing with a GM. A GM will never ask you to do anything that would compromise an account or its contents. Though the GM's motives may be unclear, there may well be a valid justification for the request, but the GM may be unable to articulate this for various reasons. Rather than disobeying in protest against the request being made or the action being taken, please oblige him/her and later express your concerns to the WoWGMFeedback-US@Blizzard.com email address. Emails sent to this address go directly to the Senior and Lead GMs, who will investigate and address any instances of potentially inappropriate GM actions.
GMs will make every attempt to show you the respect you deserve as a valued customer. We ask that you, in turn, show us the same respect. We take no joy in assigning account penalties, but sometimes must do so to preserve the integrity of the service. We look forward to our interactions with the players and hope to resolve issues quickly and painlessly so you can get back to enjoying the game.
"In contrast, I know nothing about Techlead's role in the company: Whether he was senior management or someone with a bit lower position on the company. Perhaps he overstood his bounds a bit? Or perhaps not. It makes more sense to me, though, that GM's would have more knowledge/power on this sort of topic. They actually have access to modify game data as they deem appropraite for the business, including banning people from playing the game, and they have a legitimate business reason to be doing these things. CM's on forums, on the other hand, would have a business need to be able to post to a forum, and probably to ban or suspend people from the forums if they misbehave on the forums. When people talked about Eyonix's playing with a person named Chode, Eyonix directed people to take up the matter with GM's if they had an issue with it. That's right, the CM directed people to talk to the GM. So, in the end, I'm more likely to look at a GM's statement made directly to me rahter than a statement buried on a forum somewhere.
Importantly said about this topic, it does not seem that Blizzard has started banning people, and if a ton of people keep asking Blizzard (and drain their corporate resources by spending paid-for labor answering to this topic), then Blizzard is less likely to ignore the issue and more likely to respond. A public response, especially if action is taken, is probably more likely to lean in the direction of caution against supporting customized nudity, so the best bet is likely to not keep asking this question time and time again.
Some people have stated that Blizzard will start banning people, but then after some time it still hasn't happened. It seemed to be popular speculation, but not something that's been done.
Ultimately, though, Blizzard could detect known skins and take whatever action towards a person's account that Blizzard wants to. And so, I take no responsibility for the results of an account that arise from decisions that someone else takes.
3:03pm June 22, 2006, an Allakhazam post quoted how the most commonly used technique used by nude patches was a technique also used by cheaters who would remove gates (and thereby affect Battlegrounds matches). Version 1.11 therefore removed the easy method of techniques. However, there wasn't any news of official statements by Blizzard against the nude patch, and there was another technique also available (which was generally overlooked before) that allowed a new version of the Patchin' Batch to be once again supported nudity in WoW. (This version of the Patchin' Batch had nudity working within days of version 1.11's release, and was publicly released within a week of version 1.11's release.