When you edit a survey result as described, the node you edit remains, and a new one is created, not 'changing' the one we wanted, but keeping it, and creating a new one, thus, deleting the first result node posted...
For example:
In 'Survey->Results->All Evaluations', we have this:
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Anonymous User Tuesday 23 February 2010 8:45:12 pm
Anonymous User Tuesday 23 February 2010 8:44:40 pm
Anonymous User Tuesday 23 February 2010 8:44:29 pm
Anonymous User Tuesday 23 February 2010 8:44:26 pm
Anonymous User Tuesday 23 February 2010 8:44:24 pm
Anonymous User Tuesday 23 February 2010 8:44:21 pm
Anonymous User Tuesday 23 February 2010 8:44:18 pm
Anonymous User Tuesday 23 February 2010 8:41:58 pm

(Answers by order on input [bottom-to-top])
1: Color=Custom color (Green)
2: Color=Custom color (Blue)
3: Color=Custom color (Yellow)
4: Color=Custom color (Yellow)
5: Color=Custom color (Yellow)
6: Color=Custom color (Blue)
7: Color=Custom color (Red)
8: Color=Custom color (White)

1. 1. 1. 1. 1. 1. 1. If we edit the last one posted (nº #1) and change the 'Green' to 'Green_edited' we will have this:

(Answers by order on input [bottom-to-top])
1: Color=Custom color (Green_edited)
2: Color=Custom color (Green)
3: Color=Custom color (Blue)
4: Color=Custom color (Yellow)
5: Color=Custom color (Yellow)
6: Color=Custom color (Yellow)
7: Color=Custom color (Blue)
8: Color=Custom color (Red)

Steps to reproduce

Initialize the test case using this filter:
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--filter="eZSurveyAdminSeleneseTests.*initializeezsurvey.html"
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Steps
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Create the survey
===========
1. Log in as admin in plain admin interface
2. Click "Content structure" in top menu
3. Create a new Survey
Name : test survey
4. Create new attribute "Single/Multiple Choice"
Text of question : Color
Rendring style : Radio buttons in a row
Option label : "Red", Value:1, Order:1
Option label : "Blue", Value:2, Order:2
Extra option label : "Custom color", Value:3, Order:3
Default value : Enter custom color
5. Click "Send for publishing"
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Submit a survey
===========
1. Click the "Preview" bar below the top menu
2. Click on link to "test survey"
3. Click on radio button for "Custom color"
4. Enter custom color : Black
5. Click "Submit" button
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Validate the result
============
1. Click "Survey" tab in top menu
2. Click on "Results" icon in Survey list
3. Click on "All evaluations"
4. Click on "Results" icon to the right in "Survey result"
5. Validate that the following result is recorded:
1. Color
3 (Custom color)
Black
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Change the result
===========
1. Click "Edit" button
2. In the form, validate that "Custom color" is choosen
3. In the form, validate that "Black" is written in input field
4. Change the text "Black" to "White"
5. Click "Submit" button
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Validate the changed result
=================
1. Click on "Results" icon to the right in "Survey result"
2. Validate that the following result is recorded:
1. Color
3 (Custom color)
White
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