What exactly is meant by “This is not to say it's not a bad system”?

Question

Someone on a forum wrote

This is not to say it's not a bad system.

With some context,

This is not a component system. This is not to say it's not a bad system, but in this case you should be able to cast the pointer to any of the interfaces (or just cast it to a Gun object and it should contain the interfaces) and then use it as appropriate.

If the statement is read literally, the two nots negate each other forming

This is to say it's a bad system.

What I'm wondering however is: did this person actually mean

This is not to say that it's a bad system

or does it look like it should be interpreted literally?

Answer 1

You are correct in that the two negatives roughly cancel each other out. Literally speaking, though, what it means is the speaker is not about to "say" (i.e. voice his/her opinion) that "it is not a bad system".

Specifically this likely relates to a comment made immediately prior. Such as for example, the system having some admirable quality. In the opinion of the speaker, such an admirable quality apparently does not make up for the other potential failings of the system.

The speaker is not directly saying it's a bad system, but is saying that he/she is not saying it's a good system. E.g. "Don't mistake my previous statement for implying this is a good system."

Update: Upon reading the given context, it does appear the speaker meant to say "this is not to say it's a bad system", and it was just a mistake.

Answer 2

"This is not to say <fact>" is equivalent to either of the following:

• In spite of the previous statements, the possibility remains that <fact>
• In spite of the previous statements, one may still believe/say/assert/etc. that <fact>

In the case of the OP's question

This is not a component system. This is not to say it's not a bad system

will be read to mean

This is not a component system. In spite of this, one may still believe that it's not a bad system