Prefix and Suffix, when set on the Source, appear in the post no matter where it ends up going (Twitter, Facebook, LinkedIn, etc.) You may indicate the source of a post - "Blog", for example.
Prefix and Suffix, when set on the Destination, are only sent to that destination. For Twitter you might include a tagged user, for example.
If you include both Source and Destination prefix and suffixes, they're displayed on the resulting posts like this:
[Destination Prefix] [Source Prefix] [Item Content - Title/Body/Url] [Source Suffix] [Destination Suffix]
We've added prefix/suffix support on the source side. We continue to support prefix/suffix on the destination side as well.
Further, you can use source and destination prefixes/suffixes in a single route. If you were to use all four fields in a single route the output would be:
[Destination Prefix] [Source Prefix] Headline Body URL [Source Suffix] [Destination Suffix]
If used, the destination prefix/suffix will always appear at the very beginning and very end of the output string -- effectively wrapping the rest of the content.
This approach provides a tremendous amount of flexibility and control over prefixes/suffixes. Post away!