How can we be formed by our childhood's environment if we don't remember much of it? Studies with rats have shown that how much a pup is licked during their early childhood predicts their adult personality [1]. Also, many psychologists say that early childhood is the part of our lives where our personality is formed [2]. However, recent evidence suggests that childhood memories are actively removed, to be replaced with new ones [3]. So how can childhood affect us so much?
It all comes down to the type of memory.

Infantile amnesia is largely associated with the loss of episodic memory, a type of explicit memory that can be consciously recalled (eg, remembering a past event).  Implicit memory, such as learned skills (eg, remembering how to tie your shoes), the learned part of personality, and priming associations, are largely unaffected.

Though the reasons for infantile amnesia are not well understood, it has some similarity to retrograde amnesia, that also affects mostly episodic memory, but not implicit memory (so again, you lose memories of past events, but not your personality).  The hippocampus, an area of the brain associated with memory consolidation, is an important factor in both types of amnesia.

PS: The first article you link to is about genetics, or specifically epigenetics, that is to do with gene expression.  This is a completely different factor that is also immune to amnesia since it is not related to memory, and so far it is only implicated in a very few traits.