After the patch on T301131: Test Elastic 7.10 language analyzers is deployed, we need to reindex (almost*) all wikis to enable the change to fix the regression for "narrow no-break spaces".
This is a smaller problem, so it can also wait until after the 7.10 rollout is done. (And it'll be a fun test of the reindex process with 7.10!)
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* Monolithic analyzers are not affected, but it would probably be easier to reindex everything than trying to carve out the few that this doesn't apply to.