Indication of participation
Anonymous and registered users should be able to indicate whether they are participating.
For inspiration: This is how Mobilizon realised it.
https://docs.joinmobilizon.org/use/events/participate-event/
https://docs.joinmobilizon.org/use/events/manage-participations/
For me, this issue is not about implementing it in this exact form, but more about the possibility that people who organise events can estimate how many people will come. And they can do this even if they or their participants do not have accounts on other Fediverse services.
It should also be possible to limit the number of participants for an event.
Perhaps users need different qualities here in order to say something about their own participation as well. Indicate a general interest. A " Maybe I'll be there". Or to give a clear commitment to come.
It should also be possible for interested participants to change the quality of their indication afterwards. For example, if they have already confirmed their participation, they should be able to cancel their participation again. Perhaps with the optional choice of sending a reason for the cancellation to the organisers via a text field in addition to the cancellation button.
If it is an event with limited participation capacity, it would be my wish that people who are interested in the event could receive an automated notification that places have become available again and if so, how many.