In Slovenian language the verb form depends on the number of subjects. E.g. in English you can do composition like this "1 user" "joined the room" "2 users" "joined the room" so you reuse the "joined the room" part for all number of users. But in Slovenian the verb from the second part depends on the number of users: "1 uporabnik" "se je pridružil v sobi" "2 uporabnika" "sta se pridružila v sobi" So you can not reuse the exact same second part. One (not recommended) way of solving this is to also mark the second string as plural. But such jigsaw puzzle style of user message composition from multiple strings is not recommended at all for translation. The strings should be offered as only one string marked as plural so it is all translated as one entity. So far I could see the problem with room events, but maybe there is more.
It's probably more, I assume it would effect all the strings for how many users "updated their avatar", "changed their display name", etc. Looking at the code we might have to do this the hacky way as the reality is no part of the code knows both what the action is and how many users did it.