For everyone :

Plus, the problem is not *better* indexing (that would be great of course), the problem here is that a lot (if not most) Wikisource pages are *not* indexed!
If you type "when men went up in balloons" or "The banners rustle in the breeze" in Google (taken from the previous examples), Wikisource doesn't appear at all (and for other examples, when it does, it's incomplete and with a long delay of - at least - several months, the first example was done last week, the second was created in February!).
That's why some of us suspect something is wrong somewhere (maybe because of the proofread extension ? and that Google doesn't "see" our pages.

I've tested a bunch of non-indexed pages (some of which are from 2011) across multiple Wikisources, it shows up as "URL is available to Google'' (indicating that Googlebot can see the page). I am pretty sure that there is no issue wrt to this specific thing on ProofreadPage/Wikisource extension's side (there could be one on Google's end?)