Receptional - 7:20 am on Mar 1, 2013 (gmt 0)
There is more than one platform like this - so you were right not to mention one in particular.
I found a site that got burnt in one of these systems years ago - before penguin - although every post used the same anchor text three times on the page, so that was probably a red rag to a bull to Google.
Of course, if you feel there are "100,000s" quality blogs on the system then clearly the word "quality" has lost some of its subjectivity... as have, perhaps, the bloggers.
There ARE good bloggers on some of those systems - but they may also be the naive ones. If the network has that level of scale, then Google will already have assimilated these imho - especially if, as you say, there is code on the blogs.