Honestly it is a pretty interesting argument. Again, they are arguing this, not the OP.

No, its not. Its an r/IAmVeryClever comment.

You may as well accuse mothers themselves as unlawfully imprisoning their children against their will, either born or unborn.

The OP was saying the idea that personhood begins at conception is a poor model of reality. They are suggesting that we are picking and choosing attributes of personhood to meet our preconceived conclusions around abortion rather than making a rational assessment. They are falsifying the premise by showing its natural extension as applied to this situation.

> You may as well accuse mothers themselves as unlawfully imprisoning their children against their will, either born or unborn.

I think the OP would agree.

A kindergarden teacher is not "guilty of unlawful detainment" when they stop a toddler from wandering out of the classroom. A mother is not "guilty of unlawful detainment" by housing their young child.

OP has not made some profound statement about the personhood of fetuses. They have stumbled into the murky waters of children's civil rights and flailed about. Whether a fetus is a person or not makes no difference to their hypothetical scenario.