Is 微话题 an acceptable translation of “hashtag”?
「微話題」is literally microblog discussion topic, where「微」comes from「微博」(microblog). Note that Weibo is a proper noun also using these two characters, but before Weibo was invented「微博」was just a generic word meaning microblog.

Netizens put the discussion topic (話題) between two hashtags, much the same way the single twitter hashtag is used (possibly because Chinese doesn't use word spacings). In the sense that it is an announcement of a discussion topic on some board/forum/social media then translating it as hashtag is fine, but this translation may be confusing for people coming from the PRC if one uses it to point to "western" apps/media that are possibly banned or relatively unknown/unpopular in the PRC such as Twitter and Facebook.

See also the Baidu article 微话题.