I'm not entirely sure, the general community rules don't say anything about talking about NSFW content, however, in the thread for sharing games you have the following message:
https://itch.io/board/10022/release-announcements
No NSFW or Adult content In order to be inclusive to as many people as possible, our public community is not for posting adult content, you will have to find somewhere else to promote it.
This implies that adult content should not be allowed in the entire Itch community (I mean the forum), but the strange thing is that this is not clarified in any general rules or sections, for example, te community rules don't sat anything
https://itch.io/docs/general/community-rules
If the admins read this message and clarified it, that would be ideal, if not, in the absence of such clarification, I would advise you not to post links or images to adult content, but it is only speculation, I cannot assure you.