Latest VAX, Win7, VC2008
Create a snippet and add the "$selected$" insertion. Now create a comment and add some text. Select a word and the space in front of the word, than chose your snippet from context menu. An extra space is inserted in front of the word.
Before using the snippet
// bla foo bar
Selection for the snippet
// bla foo bar
// ^^^^
Result of snippet (note the extra space)
// bla foo bar
// ^^^^^
This happens also in normal code, but i recognized it first in comments while using snippets for surrounding special text with other text.