Date: November 6, 2012
Think of a truecrypt volume [which is really a type of logical hard drive] and it’s content, as being one…because the way it exists, it really is.
The truecrypt volume acts as a safe, for which you cannot render a readable version of it’s contents, without the proper key and the safe’s own integrity still intact.
If you delete the volume and it is recovered still intact [it’s not damaged, by being written over], everything inside of it will remain protected by the encryption.
If you intentionally delete and wipe it, then you will have damaged the integrity of the volume, making it unreadable to the very encryption software required to decrypt it [you’ve damaged it, beyond the point where it even can be decrypted]…This is why it is strongly recommended to wipe a hard drive many times over, before reformatting.
I don’t believe it is enough, to simply reformat a hard drive, if your intent is to quickly/thoroughly destroy a truecrypt volume. I think I’ve read somewhere, [given the right forensic software] the potential exists for file recovery, even after a normal reformat.
By my estimate…the answer to your question, “does [a deletion and/or reformat] destroy the barriers that stop the data within from being recovered”, is both “yes” and “no”…but nothing has really changed, concerning the question of whether or not your files are protected…other than, you’ve made it harder to recover and given enough time, it may be overwritten so many times it would be useless even if they did recover it.
It’s best to intentionally obliterate any truecrypt volumes you want gone permanently, by using software which deletes and then wipes any specified files [or hard disk areas] dozens of times over [like CCleaner]…At least then, you know it is not merely setting there on your hard drive, waiting to be recovered…because you’ve already done some serious and critical damage to it.
I may be wrong about that reformatting point, and invite anyone more knowledgeable than myself, to correct anything I’ve said here, reaffirm anything, or add to anything.