Is the `<user modes>` parameter of [`RPL_UMODEIS`](https://modern.ircdocs.horse/#rplumodeis-221) guaranteed to be a valid [mode string production](https://modern.ircdocs.horse/#mode-message) — i.e., is it guaranteed to start with a `+` or `-`? I've observed that libera.chat uses a valid mode string here, but I haven't checked any other networks.
Is the
<user modes>parameter ofRPL_UMODEISguaranteed to be a valid mode string production — i.e., is it guaranteed to start with a+or-?I've observed that libera.chat uses a valid mode string here, but I haven't checked any other networks.