Why did the Nazgûl drop Merry in Bree?

[Alcuin]

They were at Ferny’s house. Harry the Gatekeeper had seen all four hobbits, even though Ferny had not, and he had no doubt given the conspirators in the spy-ring a description of all four. In addition, Ferny and Harry had to recognize all the local inhabitants, and Merry was plainly not a Bree hobbit; indeed, Harry remarked that the Shire-hobbits and Bree-hobbits spoke with different accents. (Frodo noticed that Aragorn began speaking to him with a Bree accent, but as he relaxed his accent changed, probably to that of Rivendell or his Dúnedain kinsmen.)

Upon reflection, I think we have to agree that Merry was not mistaken for “just any old Bree hobbit.” And since hobbits are famously stay-at-home bodies, a strange hobbit at the last house – Ferny’s house –can only mean that one of the visitors of interest has wandered into the bad part of town.

Gordis suggested that the Ringwraiths might have dropped him because keeping him would interfere with their “quiet visit” to the Inn. I think it is probably because Nob was too far away for them to silence before he raised an alarm. Keeping Merry risked creating confusion enough for the Ringbearer to escape. It isn’t as if Merry or Frodo were going to tell the local authorities they were being chased by scary guys dressed in black all the way from the Shire: they were trying to be secretive, too. That meant that all the Nazgûl had to do was be certain that they knew when the Ringbearer left and where he went: just keep him in sight until

1. he left town and could be nabbed in the wild, or
2. the other seven could join them and they could arrange a proper attack in numbers sufficient to keep their quarry from escaping.

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Separate question:

Bill Ferny’s house is the last in the east end of Bree along the Road. It is clearly the “bad part of town.” Is this a reference, perhaps even an unconscious one, to the East End of London? (No offence intended to any real East-enders here, please!)

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Added in an edit: this post cross-posted with Gordis's last post and is not intended as a response to that. Carry on, and I'll respond as I am able to obtain time to prepare an answer.