From the full text of the CC BY-SA 3.0 license (emphasis mine):
Subject to the terms and conditions of this License, Licensor hereby grants You a worldwide, royalty-free, non-exclusive, perpetual (for the duration of the applicable copyright) license to exercise the rights in the Work as stated below:
- to Reproduce the Work, to incorporate the Work into one or more Collections, and to Reproduce the Work as incorporated in the Collections;
- to create and Reproduce Adaptations provided that any such Adaptation, including any translation in any medium, takes reasonable steps to clearly label, demarcate or otherwise identify that changes were made to the original Work. For example, a translation could be marked "The original work was translated from English to Spanish," or a modification could indicate "The original work has been modified.";
- to Distribute and Publicly Perform the Work including as incorporated in Collections; and,
- to Distribute and Publicly Perform Adaptations
You do have the right to have your name removed and disassociated from the work. This right is granted by clause 4a of the CC BY-SA license, specifically the sentence
If You create a Collection, upon notice from any Licensor You must, to the extent practicable, remove from the Collection any credit as required by Section 4(c), as requested.
As noted above, this does not prevent Stack Exchange or anyone else from distributing and adapting the content, merely from associating your name to that content. This is also an inalienable moral right in some jurisdictions. Stack Exchange accommodates anonymization of posts: you can e-mail
email@example.com with the list of posts from which you'd like to have your name removed.