I suggest to replace diaspora and Diaspora by diaspora* (or diaspora\*) if there is no word-character before or after it.
Like in /\W(diaspora)\W/i replace the group by diaspora\* this case it should catch all occurrences of the word diaspora even at the beginning of sentences and the beginning of lines and even including the hashtag #diaspora and if someone uses “diaspora-protocol”. But it would not affect if someone writes something like “disporians”.
The only downside imho is if someone really really means a diaspora just as in diaspora but this usage is way more unlikely but meaning diaspora*
As you say there are other use-cases from this word. It is a loan-word from ordinary language, after all, and it would definitely be inappropriate to ‘force-brand’ the word in a phrase such as ‘the African diaspora’ or ‘the Diaspora [of Jewish people]’ in a post.
There is already no need to escape the asterisk after ‘[Dd]iaspora’ or ‘[Dd]’ as a whole word, so it’s easy to add the asterisk if you want to without a risk of messing up formatting. I really don’t think we should force the asterisk on anyone who didn’t intend to use it.