Caveats with the existing TextExtracts service are documented here:
https://www.mediawiki.org/wiki/Extension:TextExtracts#Caveats
We should also surface these in the API response as warnings where possible.
[] When exsentences is used in html mode a warning should be sent to the consumer "exsentences is not guaranteed to work when used in HTML mode."
[] In HTML mode for all output show a warning "HTML may be malformed and/or unbalanced and may omit inline images. Use at your own risk."
[] The message should be configurable via messages. WikimediaMessages for instance may want to point users to the alternative RESTBase service.
= Questions
[x] Should we also point them to the RESTbase service in these warning messages?
This is up to the wiki which can customise the message.
[] Should we add `math` to the elements that should be excluded from text extracts and check that no math tags appear inside https://en.wikipedia.org/w/api.php?format=jsonfm&action=query&prop=extracts&titles=Planck%20constant ? Alternatively we keep them - as consumers can parse them and display them if they are capable of doing so.