I'd recommend using normal paths instead of connectors and snapping them to objects. In my experience, connectors were unreliable in previous versions of Inkscape.
Q2) Can I rely on Inkscape SVG to preserve the above two features that I use? Since Inkscape SVG files do you namespaces to extend features, most XML applications shouldn't have issues and will just ignore the extraneous data. The primary use-case for it is if you need to process an SVG file by another application that chokes on all the inkscape namespaced stuff. Plain SVG generated by Inkscape is generally not useful. If you save as a plain SVG, make some changes, and then press Ctrl + S, it will be saved as an Inkscape SVG, not plain. Q1) Is the default SVG format the plain SVG, i.e., when saving, either with File->Save or by using ctrl-S? I'm wondering if that explains the corrupted schematic when I re-opened my file. Plain SVG removes that special namespaced data, which is why you are seeing a formatting loss. The Inkscape SVG file format will support these Inkscape's extensions to the SVG language, assuming you are viewing the SVG in Inkscape or a program that understands those extensions. Inkscape supports these features by storing additional information that it needs in the inkscape namespace in the SVG file. SVG connectors and text flows are not standard SVGīoth SVG connectors and flow-into-frame are actually not supported by the SVG specification.