Comment # 1 on bug 1026156 from Stanislav Brabec

Weblate has the check built-in.

But the source of the string in the bug 1018576 does not specify type of
formatting, so Weblate cannot enable the correct check.

https://docs.weblate.org/en/latest/user/checks.html#check-c-format

The fix is easy:

 #: src/lib/fonts/fonts-dialog.rb:328
+#, c-format
 msgid "<p><b>Specimen for %s</b></p>"
 msgstr ""

Looking at the YaST source, it is a very more generic problem:

78 of 97 pot files contain "%" character in some of its strings.

But only 5 yast pot files use "c-format" keyword.

Weblate is capable to enable particular check for all strings in a component,
but I am not sure whether it is a good approach (configuration section Quality
checks flags). It would force the format checks for all strings, idependently
on a real use in the source. In some cases it can block correct translation (e.
g. if the string with "%" character is not used in printf()-like context).