43 characters. [fixed in v1.432]
I discovered that if you enter more than 42 Russian characters in the "your name or callsign" field (too lazy to check others, but there are no problems with English), you become invisible. No, everything is still visible in the logs. But in «admin -> status» nothing is visible. Also not visible in rx0 ... 4 for others. This is not very convenient. Probably need to limit the number of characters. I have not yet tested if it is possible to inject a script there in order to break something.