Hey, I'm only at 400s, but the wiki has told me all. Which I'm kind of glad of. If not for spoilers, I don't think I could've continued DC.
If the people you're noticing are really unimportant characters, then it's most likely blatant filler trying to not waste so much time. Maybe the "Oh, my, isn't this child smart?" is played as a running gag. The only significant incidents are with Takagi, which didn't induce as much plot/character development as one would hope. All in all, I think they're caring less and less about Conan being obvious in his involvements with a case.