Why can are the handles of node only sometimes locked in a straight line?

Question

I don't understand the logic of Inkscape nodes. What I have figured out so far:

• If I Ctrl-click a cusp node, then it turns it into a Bézier node with two handles

• If I pull a handle back into the node, then that side of the node becomes straight (i.e., cusp-ish)

What I can’t figure out is:

• Why are the two handles sometimes locked in a straight line, and other times you can move them independently?

Answer 1

Select a cusp with the node tool.

Click the cusp holding Ctrl => you get symmetric handles.

Click a node holding Ctrl. If the node had handles, they become symmetric.

Drag from the cusp holding Shift => you get an independent handle.

Click a handle holding Ctrl => the handle vanishes. There's no need to drag handles into the node.