I'm not sure that such content would count, though I'd have to review the wording of the GDPR to be sure. Its intent is to cover information about you that companies/people have collected or derived - which may not include things you have written about other things.
Even if the GDPRs "right to know what is stored about you" provisions does cover this sort of content, if they have truly deleted the it then they don't have to provide it as they don't have it to provide, and they are not compelled to keep it so that they can provide it on request. I have no idea whether they do truly delete the content in these cases or not, but they might if they've taken it offline due to a generic "inappropriate content" rule: if I deemed something posted to my site inappropriate I would want it properly gone so it couldn't be accidentally made available on my platform again due to some future cock-up on my part. Their ToS and other documentation my offer some clarity on what their policy is here.
As a side note (with somewhat insincere apologies for how snarky I am about to sound): regulations & laws aside, I tend to have little sympathy for people who keep data in an external system with no local (or otherwise independent) backup!
All the actual legal guidance I have seen says it does count, because the content can be cross-references with third parties to identify the author and the fact that they once posted this text on this service. This, if they close their account or delete the specific article the content must be purged.
> So, what are the alternatives? According to France’s GDPR supervisory authority, CNIL, organisations don’t have to delete backups when complying with the right to erasure. Nonetheless, they must clearly explain to the data subject that backups will be kept for a specified length of time (outlined in your retention policy).
It's talking about right to erasure, but it would apply for requests for personal information. They don't have to crawl through their backups for you, only the current data.
Now, obvliously, the content may contain personal data, or possibly be personal data (if it's pictures of people) and in that case I assume it would be covered.
[1] https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CEL...
Some of these are very direct like your name and address. But since other personal data can be combined to create an identifying fingerprint of you it may or may not be covered.
There's a gray area in between of course were you really need to check the legal situation, but public content on a public forum is definitely not covered.
Think about pictures: the picture of a landscape you took on a holiday doesn't identify you, but other pictures in your library might do (they contain faces, places, etc.). All together, the pictures can tell who you are and where you've been and when and with whom.
Regarding your situation and concerns of other comments...
Many people in this thread point out that marketing and creating an audience is difficult work. But I think obvious-in-hindsight solution is to always keep a backup of your own content no matter what platform you publish it on. I'm not sure how Medium interprets their rules exactly but I would be suprised if you couldn't at least link every post back to a mirror on your own blog which would let you both generate an audience and prevents you from loosing everything is medium goes nuclear on you.
As always, back up any content that you care about. Don't just backup your own content but also that of others - ever relize a youtube video you like has been taken down by a bogus DMCA claim?. Online services may have their own redundency but that doesn't matter if they decide to delete (your) content.