At that time in Italy we did not have free local phone calls, every call would be billed based on its duration.
Now imagine being a Fidonet sysop who on a volunteer basis was running a computer at home 24/7, often having a second phone line dedicated to the computer (at the time even more expensive) to make sure that your users would not clog your home landline making you unreachable all day. Plus overnight your system would need to dial up and connect to your hub and exchange all data produced by your user's discussions (echomail). All the costs were on the sysop and the national hubs in Italy would then exchange with a system running in Belgium or the Netherlands, system which would in turn then exchange with USA. Flat rates did not exist (at least in Italy), and no sysop was asking (at least in Italy) end users to contribute with money or a subscription.
That is why content was moderated in the first place, to avoid off topic discussions that would waste byte and increase the bills. For this reason you would also need to limit signatures, tag-lines and so forth to 80 bytes, which IMHO are more than enough for a signature, unless you want to add ASCII ART to it.
