Quit messages allow someone to give a reason for leaving. Filesharing allows people to share small files quickly over the net. Pinging allows you to see how much lag you have. Version replies are useful to from the client author's point of view for advertising of sorts, and for people helping someone to easily see the client and version of that person without having to tell that person how to find out. All useful things.
I have no idea what an 'annoying-ass teddy bear popup' is. I'd assume you mean a popup which draws a bear with with text. This along with all the other addon related stuff is just that, addons. They're relevance doesn't matter because they're not a part of mIRC. Which is probably why if anything, an ASL identifier should be an addon.
Finger reply. Useful for adding miscellaneous information about yourself that someone might want to know about you, like for instance.... your age, sex, and location. Wow, well imagine that. IRC clients have already provided sex crazed people with a method of showing their info.
