In InkScape, you can select your nodes and press CTRL+L in order to simplify (or click Path - Simplify).
In Moho, CTRL + M will simplify your curve between 0 and 100% but Moho is not the best tool for static images.
In VectorStyler, you can remove some nodes from paths by painting over the node.

In Xara, there is nothing. Yet you can use the paint tool (in pucker mode) to adjust your spline, then you select the nodes to remove, and finally you delete them using the delete key:
Click image for larger version. 

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