In Commander, does tucking your commander into a library with Hinder mean you can no longer send it to the command zone?

Under current Commander rules, whenever your commander would be put into your library or your hand (in addition to the graveyard or exile), you may choose to put it into the command zone instead. This replacement effect is always available to the commander's owner, regardless of what caused the card to move there.

This rule change was made official in 2014 by the Commander Rules Committee specifically to eliminate the 'tuck' strategy as a way to permanently deny a player access to their commander. Before 2014, tucking a commander into a library with cards like Hinder or Spell Crumple did bypass the command zone replacement effect, but that is no longer the case.

The relevant rule is CR 903.9, which states that if a commander would be put into its owner's hand or library from anywhere, its owner may put it into the command zone instead. This is a replacement effect that the owner chooses to apply (or not).

Example: Your opponent casts Hinder targeting your commander spell on the stack, choosing to put it on the bottom of your library. As that effect resolves, you (the commander's owner) may instead choose to send your commander to the command zone, where it can be recast for its commander tax.

So 'tucking' a commander is no longer a meaningful threat in terms of permanently removing it from the game — the owner can always redirect it to the command zone per CR 903.9.