That'd be like some site translating their TOS into French and saying, "OK, but if you read and accept the terms in the new French version then PSYCH HAPPY APRIL FOOL'S DAY FRENCH VERSION ISN'T REAL JK YOU SMELL GO AWAY".
Maybe some War of The International Lawyers took place. Russian lawyers: "Our site is for Russians. It's in Russia. It's in Russian. Only Russian TOS is valid!" US lawyers: "A tremendous amount of your userbase resides in the US and other English speaking countries, so the TOS must be available in English." Russian lawyers, pouncing upon the word "available": "Fine, TOS will be in English! But only valid in Russian!" US lawyers: *cursing, stomping out*
Imagine DW tries this - we start to offer two TOSes: one in English, one in Russian (we have a growing Russian userbase, so while it's not inconceivable, it's still pretty unlikely - but don't you never say never). But PSYCH HAPPY APRIL FOOL'S DAY RUSSIAN VERSION ISN'T REAL JK YOU SMELL GO AWAY
The thing is, I don't think that's even possible under US/English common law. The TOS could be in 99,473 languages, three of them Martian, and it would still be binding, as long as it was the same TOS.
If it was a different TOS (what I suspect happened over at LJ with the English version - that it's different from the Russian) ETA2, 4-13-17: it's the same TOS; see darkoshi's response and the link they add for further reading, then in the US what would happen next is we'd have one big lawsuit to determine which TOS, if any, might turn out to be the valid and legal one.
At least, I think that's how it would work. But I'm not sure they covered this in high school Business Law, which I took approximately five bajillionty years ago, so don't quote me!
ETA, same night: Having an "Oh, I get it" moment, I think: maybe they mean it's only valid as it applies to Russian law, so the parts of it that wouldn't be legal ("valid") under Russian law anyway will simply remain "invalid", so if the English TOS allows anything legal in the US that's illegal to do in Russia (such as posting pro-LBGTQIA content) then it's still illegal to do on LJ - from any country - no matter which TOS you're looking at. But rather than say, "Our law beats US and all other law because we said so" they say, "Only our Russian TOS is valid".
OK, so let's reverse this (I'm about to offer a completely nonsensical example): say talking about BitCoin is illegal in the US but not illegal in Russia. Bizarre, but let's just say, and DW has - in this non-existent, completely fictitious example that contains some completely non-existent things - two TOSes, one written in English, one in Russian. DW's servers sit in the US, and the userbase mostly speaks English, so our TOS says, "Talking about BitCoin is illegal, so don't do it" but the Russian TOS says, "Talk about BitCoin until you go blue in the face!" Obviously, the Russian TOS rule about BitCoin is illegal in the US under the nonsensical law I just passed without an act of Congress, so it can't (or probably shouldn't be, if DW's owners wish to avoid trouble) be done by any DW user - from any country. So in any situation where our TOS, as written in Russian, allows illegal activity as defined by the US, nothing changes - that thing will still be illegal to do.
Which - if that's the case - sort of makes sense, but if so then holy shit, why didn't LJ just say so.
ETA2: though I've crossed out the now-irrelevant parts, this isn't a settled question for me. What about BitCoin being illegal to discuss here but not there? I do wonder which TOS and which laws would take precedence in that case, or if both TOSes would be struck down as "invalid" simply for not saying the same thing to all users. Which country would have the authority to strike either TOS down? *jumps down rabbit hole*
In US, you read TOS. In Russia, TOS reads you (bad, bad fucking joke - I wish there were better ones for this)
ETA2, 4-13-17: based on darkoshi's response and the link they add for further reading my first ETA appears to come to the right conclusion - with the big difference being that the TOS does say the same thing in either language but how it's interpreted could depend upon how it translates from one language to the other, so SUP apparently decided the Russian version should take precedence, probably because SUP's servers are now sitting over in Russia.