I want match pages which have actually curly braces in the names (like this one), but this matches a lot of pages without the braces in their names :( :

[[!inline show="3" feed="no" archive="yes" pages="*_{*}_*"]]

(note: the inline above has been restricted to 3 matches to keep this page
concise. Hopefully it is still clear that this page is not in the output set,
and the 3 pages in the output set do not contain curly braces in their
titles).

When escaped, it doesn't work at all:

[[!inline show="3" feed="no" archive="yes" pages="*_\{*}_*"]]

[[!inline show="3" feed="no" archive="yes" pages="*_{*\}_*"]]

More tests:

"\*{\*":

[[!inline show="3" feed="no" archive="yes" pages="*{*"]]

"\*\\{\*":

[[!inline show="3" feed="no" archive="yes" pages="*\{*"]]