some people enjoys it, some people doesn’t. from wikipedia:
Spamming is the use of messaging systems to send multiple unsolicited messages (spam) to large numbers of recipients for the purpose of commercial advertising, for the purpose of non-commercial proselytizing, for any prohibited purpose (especially the fraudulent purpose of phishing), or simply repeatedly sending the same message to the same user.
the keyword is unsolicited: you don’t want it? just don’t add it to your communities. you want it? add it to your community. it doesn’t bother you at all if it’s unsolicited.
A possibile solution might be to link the post uploading the image to the image itself, and if the post gets deleted the image should be as well deleted, or “hidden” somewhere if the post should be un-deletable. This way removing the post wouldn’t allow people to still view that image, hence it would be unuseful this “trick”