So I’ve a sort-of reply to my very own query.
First the app at https://github.com/sbarex/SourceCodeSyntaxHighlight appears to repair it for me by explicitly offering quicklook for a lot of varieties of textual content supply information (maybe too many!)…
Nonetheless, after putting in it after which uninstalling it as a check, the “TipsAppQuicklook” message appears to go away for some — however not all! — file sorts, however nonetheless with out really displaying the preview window.
Having observed this behaviour after deleting the syntax highlighter app, I attempted some extra deletions. First, I deleted TextMate. Nonetheless no preview, however the button modified from “Open with TextMate” to “Open with TeXShop”. So I deleted TeXShop. After which… it labored (i.e., unhighlighted full window preview with an “Open with Bbedit” button)!
However I nonetheless wished TextMate, so I reinstalled it (and TeXShop, though I actually do not use it) and… it nonetheless labored! It nonetheless had “Open with BBedit” however I used to be capable of change that with the “Get Information” dialog. It is not excellent: no syntax highlighting, and css information nonetheless do not present a preview, and it appears to be brittle concerning opening with BBEdit vs TextMate, which appears to typically trigger it revert to the unhealthy behaviour, however it is perhaps an sufficient answer (although I may very well return to the brand new syntax-highlight app).
Clearly there may be some dependence of all of this on the order of set up of the functions and the way they register their capabilities which can lead to clashes. I ponder if it is documented wherever and if there are much less sledgehammery methods to alter the way it works….
