I'm not a particular admirer of E.D. Hirsch, but the distinction he
offers between meaning and significance _could_ provide a legitimate
'place' for individual readings which many might see as having little
basis in the text. There could then be reasonably rational (i.e.,
sharable) perspectives both on the meaning and on the significance
different readers find in a poem. For example, Steve's comment in his
second post:

Well, I think the phrase means just what you you're afraid I think it
means. The image of the fog is dog-like (or cat-like), and I have a
mental image of people in some doggie-style sexual position. The phrase
'let fall upon its back' then follows. The sexual imagery continues in
"licked its tongue". And, at the risk of being overly graphic, liquids
deposited during sex will un-deposit themselves, forming "pools". I'll
let you decode the rest of "the pools that stand in drains".****

Now I think it is correct to say _both_ "You can't claim there is an
image of dog-like sex here" _and_ "Obviously one _can_ say it because
Steve just did." That is, there was a point in Peter's response to Nancy
on this phrase, but the real point was lost in his heavy-handed sarcasm.
The idiomatic use of the phrase is commonplace and quibbles are
ridiculous. It is _also_  worthwhile taking it literally and noting
that, in a given case, it is perfectly possible to make such and such a
claim, and that possibility needs to be accounted for. I myself don't
believe for a minute that there is a homosexual subtext (or hidden
meaning) in "Prufrock," but it is a fact about the poem, a fact worth
treating with respect, that at least one reader can find such thematic
material in it. No one would claim that it was a poem about the anger of
furniture store clerks when people sit on the couches -- and if someone
did rather than argue I would accuse such an account I would accuse
him/her of being a liar. That is, I sould seriously claim that no one
_can_ offer this gloss. The poem simply won't allow it, and anyone who
claims to find it there is lying about their own experience of the poem.
I don't think we want to call Steve a liar, and he is clearly not
mentally deficient or utterly ignorant, so his interpretation (I would
say the significance he finds in the poem) is a fact about the range of
responses the poem's text allows -- and a construal of the poem's
meaning would ideally allow for this fact. There is no need to jump on
Steve; rather, even if one rejects out of hand that the poem has a
homosexual content, one can profit by Steve's response to see the poem
more fully.

Take another example, my own response to "Gerontion" as an "echo
chamber" rather than a dramatization of a character. The poet (outside &
inside the poem) sets fragments of the European past & present jarring
against each other within that echo chamber - Cleopatra's vagina
identified and/or confused with the twists and turns of the history that
crashed in ruins at Sarajevo.

Suppose  I propose that response as a significance I find in the poem.
Then the discussion could revolve (for example) around what aspects of
a  more constrained reading of the meaning offered linkage for the
proposed significance. Such a discussion might or might not get anywhere
in the sense of a conclusion, but it could throw off interesting
questions along the way.

I couldn't understand why Jennifer had to express her disagreement on
interpretations (in which she made what seemed good points) in the form
of a general tirade -- and I didn't see why Peter had to get sarcastic
about Nancy's phrasing. At the conversational level appropriate to a
maillist, it would have been legitimate to play with different senses of
"I don't think you can" -- i.e. explore it as a literal rather than an
idiomatic phrase, but it seems a bit churlish to attack the phrase as
though it could only be literal.

Again, I'm mostly letting my fingers do the thinking for me here. But
perhaps this will suggests a few paths of discussion.