I want to start out with two key points.
Firstly, I don't 'support' piracy, but without it there is no doubt that I wouldn't be this involved in the visual kei scene (and possibly probably not even where I am in my life right now, since listening to Japanese music back in JHS is what eventually led to me formally studying the language and now living and working in Japan, but that's a long story for another thread).
Secondly, I voted that piracy is instrumental in keeping the scene alive, but I only believe that to be the case in the international fandom. I would argue that it has little to no impact whatsoever on the actual living scene here in Japan, at least in my experience so far.
With that said, I'd like to go into a little more detail. Obviously piracy has been existent since the early days of home media - my uncle used to buy pirated VHS tapes of new movies when I was a kid, for example. With the arrival of the internet, and subsequent developments that have drastically improved our capacity to both upload and download data, it has increased the ability and reach of piracy to a global scale. And despite the cherry-picking of various studies to pin the blame for unsuccessful media on the illegal file-sharing community, the evidence shows that for the most part there is little to no impact whatsoever on sales as a result of piracy.
The reason that I think piracy is essential for the international visual kei community is simply a matter of exposure. With communities like MH which share the latest news the moment it leaves the artist's mouth at a concert, or the second it's posted on social media or their official website, even the newest and smallest indie visual bands instantly get tens, hundreds, maybe even thousands more people's attention than they expected. But even with that awareness of band activity, there's no promise that the international community will put their money where their ears are and pick up their releases. With inflation increasing the sales price of CDs over the last few years in Japan, and the fact that many small VK bands release music only in independent record stores or even exclusively at concerts, simply buying the music you're interested in from half way around the world becomes a tall order. This is only compounded by the fact that on top of the costs of buying and shipping the item to you, it's likely that you have no prior way of determining whether you will really enjoy a release or get your money's worth. Hence, piracy becomes a method for fans who are willing to shell out for their favourite artists to sample and sift through the latest music to choose exactly what they put their hard-earned money towards.
However, this is speaking from a purely international standpoint. The truth of the matter is, domestic artists in Japan are not expecting to rely on international sales to any extent, regardless of the genre. This is particularly true for indies visual kei, which is far more concerned with gathering a dedicated fan base on their home turf who will repeatedly spend money on tickets and goods, where they make a lot more money than the pitiful cut they get on CD sales. Even bands that are aware of their popularity overseas will very rarely have the opportunity or financial security to consider promoting or performing there, especially on an indie label. For anyone short of a major record deal, purchases from abroad are probably like an unexpected bonus, and nothing more.
But the main reason I think piracy has little to no effect on the visual kei scene within Japan is simply that I don't think it's as common. In theory Japan has quite strict laws on illegal file-sharing, and the truth of the matter is that VK is not very big even in its home country. The scene was at its peak years ago when the philosophy of the frontrunners was more relevant, and media exposure was higher. Even if someone were to upload a new release, I just don't think there would be that many people to download it. The hardcore gya will jump on the latest release from their favourite artist, and anyone else is probably just not interested.
That's not to say that the scene is necessarily dying out though; if anything, the spread of the pre-owned market to online sales and auction sites (looking at you in particular, Mercari and Yahoo, with simple transactions and free accounts) provides a mecca for domestic and international fans alike. In particular rare items like live-distributed singles and signed goods can sell for tens of thousands of yen if the right buyer is on the lookout. It's easier than ever to get hold of VK music, and while the artists themselves don't see any financial benefit from second-hand sales, they do see an increase in exposure. In addition, devoted fans shell out time and again for not only multiple versions of releases, but also goods from clothing and towels to cheki, which are virtually like trading cards to the hardcore bangya. I would argue that the live scene and sale of goods is what really keeps the VK scene afloat, especially at the indie level. If no-one attends a new band's lives, it's far more damaging for them both financially and in terms of reputation than not selling out a 500-copy press of their first single (ignoring recording and production costs, of course).
I realise that this post has gone on for far too long now, but in summary: piracy is a necessary evil for the international community, but largely irrelevant to the success of the artists themselves and the scene in Japan.