Where a new account starts
Steam sign-in creates the account at 1,200 Rating Points, rank 3, Vanguard, with no wins and no losses.
This page explains the written ladder. It does not apply a match, and it does not change a stored rating.
The opening mark
1,200 is the floor of Vanguard. Operative and Recruit sit below it, so a new account starts in the middle of the early ladder, not at the bottom.
Signing in again does not reset a rating that is already stored. The first 10 recorded matches are placement: during them the rating cannot rise above tier 5. The codex does not invent a win-loss record.
How to see it
After Steam sign-in, the dashboard and the ranks board can show the stored rating. If the database is unreachable, the page says so instead of inventing a number.
The starting rank stays Vanguard until a recorded result moves the rating out of the 1,200–1,299 band. No such result is written from this site today.