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Conversations User Guide - To register or not to register?
If you choose to register on the site, then there are some advantages and it only requires a username and password. For a start you know your details won’t be sold on - I mean, look whose site it is.
But registering allows you to put up a picture you might like, so others can find your posts more easily, it also shows your posts under “All recent Activity” and, perhaps most usefully, it shows all the posts you've made, starting with the most recent, so finding your way back to a post you made is very simple.
You can check your history, find your previous posts to check if anyone has answered any questions you might have asked and even see if anyone has given you a mention in one of their posts.
Best of all, perhaps, you can set preferences - your interests, whether you want to receive text alerts and whether or not you want to subscribe to a Topic.
It also enables a useful feature whereby if you double click on the avatar of any registered user all their posts are promptly displayed.