Few different approaches you could achieve this. Two ideas below that you could look into:
Web AppBuilder and Related Records
- Setup a separate related table against your routes. (i.e. 1 to many)
- Publish to a hosted feature service, disable ability to update geometries and just allow edits to attributes.
- Add the Editor Widget to Web AppBuilder and configure it to allow inserting new records in the related table.
Combination of Web AppBuilder and GeoForm Template.
This would be a good option if you want to capture a series of questions from the end user in a form based interface.
- Calculate midpoint of each route and add this XY information to each route.
- Web Map with a popup that launches Geoform App URL in a new tab, but also includes the lat/lon from step 1.
- Have a web app (could be AppBuilder, or a suitable Web App template).
- The popup launches GeoForm using a dynamic URL parameter to create a new record at that location. Hide the URL from the user behind some friendly text like 'Submit Feedback about this Route'
- Optionally hide other records created by other users in the GeoForm app
- Gather feedback as a new point at that location.
Variation on this might be to not use lat/lons, but use URL parameters for feature layer searches setup against your routes layer by the route ID.
Search for areas of land they want to comment on (via a layer level search setup on the webmap) - see searchLayers in the defaults.config
Here is an example that is not actually complete - the URL parameter has not been setup to load Geoform at the same record that was just selected but it is possible.