It's about context and readability. The more implicitness you work into your language, the less you know about a block of code just by reading that block.
Sure, but that doesn't make features like this automatically bad -- it's a tradeoff between completely local understanding and extra specificity that may or may not be helpful. For example, most languages will implicitly choose a meaning for "+" (integer addition, floating-point addition, etc.) based on the types involved. That's usually a better choice than making the programmer write (and read) a more specific form like "Float.+" or "Int.+".
Oh definitely, I'm not disputing that. It's a spectrum, and different people will be more or less comfortable with different amounts of explicitness/implicitness. The grand-something-parent was talking about "implicit implicits" which... without some more context (heh), sounds like it might be a bit off the deep end.
