This does seem to divide people. My own instant response to the favourite system was that it was obviously a means of expressing approval, without bombarding yo

This does seem to divide people. My own instant response to the favourite system was that it was obviously a means of expressing approval, without bombarding your followers' timelines with other people's stuff. "This tweet is a favourite of mine" = "I like this tweet". Eventually somebody favourited one of my tweets and I got an email telling me they'd done it, which just reinforced this idea for me. Then after about 4 years somebody pointed out that it actually stored your favourites. And that meant you could use them as a kind of bookmark. Well! Who'd have thought? (I don't use Internet Explorer, which is my excuse for not spotting the favourite = bookmark connection.)