You've seen this clown makeup picture on the feed, I'm sure. It is a direct result of the issue in this jira. The picture on the left is what the skin should look like, and what it currently looks like. The picture on the right is what LL wants to do to the way skins are handled- that's the exact same skin being worn in the picture, the only change is a viewer that uses the new system.
What happened? Well, someone at LL had a brilliant idea to change the layer order skins have used since the system was devised. The system skin makers everywhere have worked under for years, and the one that they have made decisions on regarding how their skins work under the entire time they have been creating skins. What this means to you:
No mod skins: if the skin maker didn't change settings that meant absolutely nothing to them under the previous system, you may be stuck with huge ridiculous clown makeup, that is flat and badly shaped, so it is messy and ugly even if you did want to change things to that colour. And you have no choice in the matter, period- you can't make it smaller, you can't change the colour, nothing. If the skin maker is still active in SL, you, and hundreds of other people, can IM said person for replacements. As there will be a huge backlog as they are fulfilling everyone else's requests as well, you may have to wait a long time to get a replacement just because of your place in the queue, as well as the fact that that skin maker will have to spend weeks fixing things for a stupid "feature" LL decided to randomly implement without consulting any content creators, instead of making new pretties. If this change goes live, expect most skin makers to not be releasing anything for a while.
Mod skins: you will have to go into Appearance and fix all the skins with the problem yourself. If you have a bit of a skin habit, this may take you a while you could be spending doing...I don't know, anything else?
Tintable eyebrows: will be no longer be tintable correctly. All eyebrows in tintable skins will become the colour of the base "skin" colour. If the skin is mod, you can change it, however you have nowhere near as much flexability as in the system where you could mix hair and skin colour to get the perfect shade (for instance, for those of us who like unnatural hair colours, the option to tone down from bright fucking neon is no longer an option. Nor is BLACK, as skins don't go all the way to black).
Tintable makeup: some skins take advantage of the very messy under layers to allow you to change your lipstick or eyeshadow with sliders- by carefully alphaing around them, and overlaying over to make them look less flat and lousy. These skins become completely broken, as the underlying skin tone is generally not what you're going to want, and it is the only thing you'll be able to do with them.
This change has NO POSITIVE ADVANTAGES. Built in LL makeup is applied extremely messily, and is in fact a big part of why the skin market is as big as it is, and _everyone_ wears skins on the tattoo layer instead of using the built in LL skins.
This change is not currently live, so you will not see the disasterous effects in person yet. If you use Coolviewer, or one of the other progressive non LL viewers, you may see it, however, it has not yet been implemented with the official viewer. So you will not see this change yet, but it HAS been changed in house, so they can push this forward with a future release. Please, I urge you to vote on this issue to convince them to NOT put it into effect, but instead change things back to the way that actually works. Breaking massive amounts of content without any advantage? Not cool.