See https://github.com/prometheus/proposals/blob/main/proposals/2023-11-13-utf8-migration.md#mixed-format-scenarios

This bug is for making changes to the read path of Prometheus so that it returns the correct answers for questions asked about UTF-8 metric names and labels. Specifically, it might be asked to find those names in data that was written with an older version of prometheus and is escaped.

@dimitarvdimitrov had several useful questions and comments, I will paste them here.