"It takes two days."
I think your Japanese friend might have been trying to make the exact opposite point: that ついたち is the only one not used for it. ^^
ついたち has a meaning more like "beginning of the month". It doesn't have anything to do with number, so therefore isn't all that handy for durations.
For durations of days, my understanding is that it goes いちにち, ふつか, みっか, よっか, いつか, むいか, なのか, ようか, ここのか, とおか.
It's not that she cares about the points. Negative posts tend to get even more negative points down the track. So genuine helpful posts that get randomly downvoted at one point might go down this route. It's about making helpful posts more visible. It's interesting you were not able to see this. It doesn't take a whole lot of insight to see this.