I was able to answer my own question via their Zendesk (from 2016), for those interested. It looks like I just had not come across the issue, but articles were

I was able to answer my own question via their Zendesk (from 2016), for those interested. It looks like I just had not come across the issue, but articles were previously not being saved server side with the exception of those manually emailed. https://instapaper.zendesk.com/hc/en-us/articles/227342887-What-are-my-Instapaper-storage-limits- https://instapaper.zendesk.com/hc/en-us/articles/227342887-W...