If I were to use Farseek to get a shockland and put it onto the battlefield tapped, can I untap it by paying 2 life? Or does the wording "if you don't, this card comes into play tapped" prevent this?
You can pay the life if you want to, but the land will still enter the battlefield tapped.
The default way that a land enters the battlefield is untapped. Anything that states otherwise is a replacement that modifies this state into something else (such as entering tapped.) When you Farseek for a shockland, two replacement effects tell you to put the land onto the battlefield tapped - Farseek's and the land's own ability. The shockland's effect lets you pay 2 life to ignore it, but this only lets you bypass the shockland's effect - Farseek applies a separate effect that will cause you to put it onto the battlefield tapped regardless.
If people are sick of reading about stuff just stop taking part. You have 100% control over what you read. Simic Ascendancy isn't going to get banned just because you didn't tell someone to shut up on the internet.
W may only be paid with white mana. U may only be paid with blue mana. B may only be paid with black mana. R may only be paid with red mana. G may only be paid with green mana. C may only be paid with colorless mana. 1 may be paid with white, blue, black, red, green, or clolorless mana.
I know this is going into the realm of nitpicking, but 110.6b isn't talking about replacement effects at all.
I asked about this on the wizards community forum, and the opinion was that it's not a replacement effect, it's simply a one-shot effect that instructs the player to do something.
As Hendrik pointed out, it is technically not a replacement effect.
It doesn't change the answer to the original question at all, but you are correct on that point.
That said, I think this has gone as far as it should.
The default way that a land enters the battlefield is untapped. Anything that states otherwise is a replacement that modifies this state into something else (such as entering tapped.) When you Farseek for a shockland, two replacement effects tell you to put the land onto the battlefield tapped - Farseek's and the land's own ability. The shockland's effect lets you pay 2 life to ignore it, but this only lets you bypass the shockland's effect - Farseek applies a separate effect that will cause you to put it onto the battlefield tapped regardless.
the battlefield . . .” are replacement effects
As Hendrik pointed out, it is technically not a replacement effect.
It doesn't change the answer to the original question at all, but you are correct on that point.
That said, I think this has gone as far as it should.