>If things are fine as they are in any given situation, e.g. the Grafton Hill's array of street names, telling someone not to intervene to make a change is sensible.

So literally your only argument is that all change is inherently bad and has to be hyper-justified. There's a lot more examples of that in the city for you to freak out about than just the name of one street. Frankly I'm just disregarding this argument entirely, in the wake of all the changes Worcester has gone through I think pretending anyone cares about one street name is truly disingenuous.

>The fact that some people here, yours truly not included, don't know the history is further proof of the argument that no one views "plantation" in some historical sense.

You can know the connotations of the word "plantation" without knowing the specific history of Quinsigamond plantation. This is like arguing that if you know what a castle is, then you must know the history of Windsor castle.

>not the slavery that didn't even exist in the area when Quinsigamond Plantation was named.

As established earlier, there was slavery in the area - the enslavement of Native Americans. Like I said, nobody who's mad about this change knows anything about the history of Quinsigamond Plantation, including you.