For the record, fastboot flash recovery recovery.img returns:
>fastboot flash recovery recovery.img
target didn't report max-download-size
sending 'recovery' (5688 KB)...
OKAY [ 0.187s]
writing 'recovery'...
FAILED (remote:
partition 'recovery' not support flash)
finished. total time: 0.219s
@humorkritik What’s the end of the story? 
Edit: For the record, I just updated the xda guide “when you totally bricked…” after having done some thorough testing for someone else. I found out that the latest confirmed-to-be-working version of SP Flash Tool was v5.13.32 and I downloaded it here from Mediafire. Everything worked fine with this version.