Honestly, I don't really get what kind of person Mixi users mean when they say 'weird person.'
Literal
Purely, Mixi users [subject-が] say [place-ところの] 'weird person' [quotative-って] what-kind-of person is-[question-のか], I [dative-には] not-quite not-understand-[explanatory-のだ].
Casual musing with some nice syntactic moves. ~の言うところの is a set phrase meaning 'what X calls, what X refers to as' — literally 'the (thing in) place that X says.' Useful for citing in-group terminology. いまいち ('not quite, not really, lacking something') is a colloquial adverb for incomplete understanding or satisfaction. ミクシィ (Mixi) is an early Japanese social network that was big in the mid-2000s. ~なのだ is the explanatory ending.