I just wated ~one hour of my life debugging a TpContact avatar "issue". Turned out I was asking for TP_CONTACT_FEATURE_AVATAR_DATA to my factory but not TP_CHANNEL_FEATURE_CONTACTS so I wasn't getting the avatar (but was getting the TpContact from the TpChannel making it harder to catch). If a reasonably experienced Telepathy developer wastes so much time on this, there is probably something wrong with this API.
I've made a suggestion about this for 'next' in bug #49371 comment #5
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