Comment 2 for bug 1250997

Pressing the modifier 'Ctrl' while deleting selected node(s) is not working for you?

Robert Martinez wrote:
> The change of node types on the other hand isn't.

The provided screenshot (before/after) does not show a change of node type (all cusp nodes before and after). AFAIU you are asking for a feature to preserve the state (length, angle) of the _handles_ of the adjacent nodes (cusp nodes can have extracted or fully retracted handles). This feature already exists (press 'Ctrl' while deleting the selected node(s)).

The feature to preserve the shape by default is intentional and not a bug, and a modifier to preserve the state of the node handles already exists. The default mode can even be switched in the preferences:
Preferences > Tools > Node > Editing preferences: [ ] Deleting nodes preserves shape)