8:10 AM
This question was posted today:
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Let $f, g : X \to Y$ be continuous functions. Assume that $Y$ is Hausdorff and that there exists a dense subset $D$ of $X$ such that $f(x) = g(x)$ for all $x \in D$. Prove that $f(x) = g(x)$ for all $x \in X$. Here is what I have so far, Proof: Let $f : X \to Y$ and $g : X \to Y$ be continuous ...

I am pretty sure that there are plenty of duplicates.
Maybe some answers to this question (probably seeded) would fit:
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Akhil showed that the Cardinality of set of real continuous functions is the same as the continuum, using as a step the observation that continuous functions that agree at rational points must agree everywhere, since the rationals are dense in the reals. This isn't an obvious step, so why is it ...

But I guess we could find a few better candidates for duplicates.
1

$$\textbf{PROBLEM}$$ Suppose $f$ and $g$ are two continuous functions such that $f: X \to Y$ and $g : X \to Y$. $Y$ is a a Hausdorff space. Suppose $f(x) = g(x)$ for all $x \in A \subseteq X$ where $A$ is dense in $X$, then $f(x) = g(x)$ for all $x \in X$.  \textbf{ATTEMPT...

2

Let $X$ be a topological space and let $Y$ be a Hausdorff space. Let $D$ be dense in $X$. Prove that continuous functions $f, g : X \to Y$ which are equal in $D$ are equal in all $X$. I'm a little stuck with this elementary proof. All help appreciated :)

There is also this one, which was closed as off-topic/homework PSQ. (I would prefer closing as a duplicate, but it probably does not matter too much.)
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The following problem is from Munkres's Topology (exercise 13 in section 18 "Continuous Functions"; page 112, 2nd edition). Let $A \subset X$; let $f:A \to Y$ be continuous; let $Y$ be a Hausdorff. Show that if $f$ may be extended to a continuous function $g:cl(A)\to Y$, then $g$ is uniquely...

I voted in some direction. Feel free to vote in a completely different way. (Especially if you find a better candidate.) IIRC the software should prevent loops and questions closed as duplicates of each other.

12 hours later…
8:54 PM
Yes, I think that in 2015 we should start a new Reopen/Undelete thread, and a new Tag Management thread. Not necessarily "cleanup", because sometimes tag creation is proposed too.

2 hours later…
11:05 PM
Or, we might just close the old one for good. It is a source of trouble too.
Somewhat recently there was a discussion where the opinion that it is obsolete a bit was voiced.
5

There is a thread that is used for reopen requests Requests for Reopen & Undeletion Votes, etc. Some users do not use this thread for their questions on closed or deleted questions. A main reason could be ignorance about the existing thread; the question is not even tagged faq nor is there any...

more specifically
@Najib I quote: "But then, isn't that precisely what the reopen review queue is for?" Yes. It is. Note that the Req. for Votes thread predate review queues by at least a year. We essentially invented the queue! I am personally of the opinion that that post has outlived its purpose. But sometimes old habits are hard to break. — Willie Wong Nov 11 at 9:48

11:36 PM
Well, I would say that there are still cases when reopen queue is not sufficient. (Of course, I might be wrong.)
Especially with robo-reviewers and many people having differing opinion what should be re-open and what shouldn't.
I don't think that the question I mentioned above would have been reopened only through the review queue.
(The result of review was leave closed. Is there much of a chance, that many other users would notice the post in review history or stumbled upon it in some other way?)