I tend to think this question could be construed as more rhetorical than factual. Inasmuch as ambiguity can be, and often is, intended to mean different things to different people. To some analogous writing is by itself ambiguous. To others it is intended to be a prime essential. Nowhere does one realise this more than when reading poetry. Few poets can resist the temptation to titivate and tantalize the latent poet trapped within ourselves by such a ploy, but a good Poet will always give the reader a few pointers as to his intentions.
Surely it is only the moronic devoid or completely ‘empty’ headed reader, who refuses to accept or understand lines that are seen dependant upon a simple descriptive simile or analogy? But one must demand there be clues that simplify our interpretation of a piece? Without some small hint or indication, the piece would be meaningless to most everyone. To be analogous is surely an integral part of all languages, whether written or spoken. What dull fellows we would be were we to be completely pragmatic and un-imaginary in all our speech and writings? It is the essence of good writing be it poetry, prose or story telling.
Where would such great playwrights, and poets such as the "romantics" be? Shakespeare's “Shall I compare thee to a summer’s day” is a typical example - were it not for their imagination and ability to use ambiguity in its subtlest forms, the whole understanding of this poem would be lost.
But yes, of course one must separate the intentional ambiguous writing from the unintentional. Cause of many problems here I believe, is the tendency of many authors to punctuate incorrectly or use a word incorrectly. Punctuation is very important if the reader is to receive direction from the author. A comma here and there as suggested when we speak, to many, means little, but when applied to the written word? It is a signpost to what the author intended and is a far different kettle of fish. Doubtless this is where much of today’s ambiguity comes into play?
For instance the old English language lesson in how to punctuate the phrase “without her man woman is a brute.” comes to mind. An exercise that was constantly drilled into me, when a student. Did it improve my writing? Not necessarily so, but it sure improved my ability to read what was written and what was intended, making my future use of punctuation more exacting! Even so, still far too many authors we read today, leave much to the Editor - who too, is often found wanting in punctuation skills. Unfortunately what they decide is then put forth for us to interpret in whatsoever manner and form we choose. Modern literature is full of anomalies and these could well be thought of as ambiguous..
The answer to the correct punctuation? Well again it depends upon yourself and what you wish it to read? It can be written either as:
“Woman? Without her, man is a brute!”
“Woman? Without her man, is a brute!”
A far different meaning altogether, and as a result, ambiguity can be seen and found in many forms. One must perforce, appreciate the meaning of words written. If delivered in a form which begs the reader to place his own meaning thereon, means little to many. Were we to see what the Poet intended without getting some direction? We would write our own poetry, in free flowing prose, to care less about that written by others. Therefore my answer to the question posed is thus: ambiguity is fine and dandy as long as at least one pointer is clearly stated. In my opinion, this will take one or more of the following forms:
The Title will give some indication:
The Poet’s opening lines must channel our thoughts towards his intention:
The (last) punch line, must reveal all!
So long as any or all of these criteria are fulfilled, it will finally reveal all ambiguity which in turn allows the reader to understand the true meaning of the writing, now clearly seen. Should this not be so? Chances are for many, the meaning remains shrouded in a ambiguous wordy morass, and at least for me, I determine that lacking indicators or signs, the Poet failed!