Since we started enabling the gtk module in openSUSE, we got many people complaining about it: it's basically too spammy because it breaks your workflow.
An example where it's quite annoying: open a .desktop file in less in a terminal. The dialog pops up. Close the dialog. Press space to see some more content of the .Desktop file. The dialog pops up. Cry.
I'm not completely sure how to best fix this, but using a notification instead of a dialog would be a tiny improvement. Long term, though, it should really be up to each app to use a GtkInfoBar to propose the font installation, I think.
This bug report is very old and based on a version not supported anymore.
Please feel free to reopen if this is still a problem with the latest version.
The module hasn´t changed since, and so yes, this is still the same problem.