When solving notes, in some cases, it is good to know the application used to create the note to understand the context and better proceed to do a map change.
I think all applications that use the OSM API to create notes should include (append) the application name. In the current state of the API and database model, the only way is to append a text, like a hashtag (#Mapy.cz, #organicmaps, #mapsme, #OSMyBiz) or a description (via StreetComplete) in the note text. (I hope the future API version will improve the notes part )
As a note solver, I have found multiple situations where having a hashtag could identify issues in some applications. Recently, I discovered an OnOSM fork has a problem locating notes in Iran, and it is placing them in the middle of the Atlantic ocean.
Identifying notes from the OSM website, it helps us to better filter the invalid notes from other sources, especially when trying to identify why some notes are misplaced or spam.
That seems like a reasonable way to track the source. As someone currently working on OnOsm.org, I will open an issue and probably submit the PR for it.
Should it be done for all comments in a note, oronly a first one?
It seems that StreetComplete too always adds that information to the note when creating it (i.e. on first comment), but not when adding additional comments (See for example 2022-03-19 comment Note: 2707832 | OpenStreetMap with 3 photos link)
I think only in the initial comment at creation time. The first comment is important to understand how it was created and the context of the note creation. Mobile applications could be interpreted as on the ground. Websites could be most probably from a computer. Other kind of notes could be interpreted as bulk creation.
Ideally, of course, ban anonymous notes (I think to create a separate topic) But in general, having dealt with the basic simple applications, we can say that all the other notes come from osm.org
(I think to create a separate topic)