while you can search within comments (ex.https://www.inaturalist.org/comments?Search&q=ANIC1), there’s not a great way to filter observations by comments.
to do the sort of observation filtering you’re describing, you’d probably probably have to filter for your genus and place on the server side, and then once you get the set of 50, you’d have to filter on the client side.
the client-side filtering could be done via script (ex. https://forum.inaturalist.org/t/search-by-tags-not-present-not-contain/49011/2), but in this particular case, since the big set has only 50 observations, i’d probably get your observations using https://jumear.github.io/stirfry/iNat_print_friendly_obs (place id=9994, taxon id=52011), and since the page can display comments, descriptions, and tags, you can just do a find on page using your browser, like so:
if you want to keep these together for future reference, i would probably add them to a traditional project or add a common observation field to all of them, which would be easier to filter for. (the only problem here is that some observers limit who can add projects or fields to their observations.)
or you could also just keep a bookmark url by id. for example: https://www.inaturalist.org/observations?id=39832611,40116850,40168699. the drawback to this approach is that it’s harder to share this with others, though you could keep the url in, say, a journal post for others to reference, if they need to.