[yorwba]

It's a pun. 和谐 is héxié in Pinyin and 河蟹 is héxiè. They differ only in the tone of the last syllable. Since 河蟹 means "river crab", the reader will probably be able to guess that some other word is meant and correct it to 和谐 in their mind.

This is not just used to evade censorship, but also humorously. E.g. returnees from overseas 海归 (hǎiguī) are frequently called sea turtles 海龟 (hǎiguī). In that case, even the tones match.