From the picture, the feature at the base of the cylinder looks like an everyday casting anomaly and nothing more. It does reach upward toward the water jacket but if it doesn't leak or isn't too thin then it is of no concern whatsoever and the block is as good as the next, capable of supporting over a thousand horsepower.
Farther up the picture, there looks to be another anomalous feature: a casting void in the machined portion of the main web. As long as that is negligible as well (ie, not to deep, etc) then that's a non-issue just the same.
In the majority of builds where this block would be used, those features may be left alone, meaning it's not even necessary to acknowledge their existence (in a build of extreme abusive power might I consider blending them out).
