What about flagging already flagged values again?
We have the situation, that most tests, won't ever be able to flag already flagged values again, as they only see the data masked. Some functions however do, mainly those working and flagging entire rolling windows (e.g. !580 (merged)) and also functions not routed through the usual masking/demasking functions.
I consider this to be a non-ideal situation and would very much prefer an uniform behavior, where functions don't ever overwrite existing flags, even though, this might need extra care while implementing these functions. The main reasons are, that I 1. highly favor uniformity in behavior and 2. see issues with the further use of such multi flagged values (question: which is the flag function to report when outputting flags in more complex flagging schemes, the first, the last, anything in between)
The goal of this issue, is not to fix all occurrences of overwritten flags, but to find a general policy how to handle this in the future.