F-Droid allows apps that have premium features, requiring a payment to be unlocked.
Some apps don’t disclose this in their F-Droid description, and others do it inconspicuously.
This leads to a process where a user looking for a suitable application, might needlessly download and install apps, only to uninstall them shortly after.
This is a waste of resources: on the user’s end of energy, time and effort, and of bandwidth for F-Droid and users both.
This change would also bring the F-Droid experience more in line with what appears to me as the norm of the web, where user-oriented sites generally use conspicuous labels for software that require payments in part or entirely (e.g. Play Store, Amazon, Steam, etc)
My humble suggestion would be to add a badge near or under the application’s name, so that it’s immediately clear whether an app is completely free to use or not, removing the need to sift through the description or install the app to find out.
Since this has nothing to do with the application’s code being open-source or not, it probably needs not be classed as an anti-feature.