See also https://commons.wikimedia.org/wiki/Commons:Upload_Wizard_feedback/Archive/2011/10#Blank_edit_summaries

Will this have effect in summaries of filters established via Special Tags, like cross-wiki uploads (see also filter 153 --> "Cross-wiki upload from" in summary") + video uploads + OAuth Uploader + etc. ?

I'm not sure why it would? I might be misunderstanding. What do you mean by "summaries of filters"?

It would have an effect on any abuse filters that would look for "User created page with UploadWizard" in the edit summary to identify uploads made with UploadWizard, but I don't think any exist now. In general it would make it more difficult to identify whether an upload was made with UploadWizard, unless we also did T121872 at the same time. (Although, we also mark UW uploads with a category, so maybe not…)

"What do you mean by "summaries of filters"?" Sorry for my misleading comment. I mean the summaries (or upload comments) in the uploads using different upload tools (see above), like (example) "Cross-wiki upload from en.wikipedia.org" which is stored in the mediawiki-table "img_description" and which can be used – via Quarry – for filtering. If e.g. this gets overwritten with License: {{cc-by-sa-3.0}} (...) it will be eventually harder to filter those uploads...

But: I probadly have stolen your (and others) valuable time, because I ignored the title of the task "(... file uploaded with UploadWizard)". My (spontaneous) concerns may be completley unrelated. Sorry for this.

Mark, if the true purpose of an edit summary were to merely identify "the process that makes the change", then custom messages that describe the change would be inappropriate: they would all simply be tagged "wikitext editor" or "edit made by a human" or "bot edit" or things like that.

Instead, ths is a request to follow what's currently the best-practice for bots, which don't merely say things like "created page" any longer. They say things like Dating maintenance tags: {{Improve categories}} (naming the specific template changed) and Migrate {{Infobox example}} coordinates parameters to {{Coord}}, see Wikipedia:Coordinates in infoboxes (with a link to further information).

This is in addition to the name of the tool (which is the username in the case of bots and which is better handled with a tag otherwise or an automatic addition to the edit summary by the tool) and the action ("created page" – which is already evident from the RecentChanges entry : (Upload log); 20:00 . . Username (talk | contribs) uploaded File:Example.jpg).

In other words, the edit summary ought to not merely repeat the information than is present in RecentChanges without it, but also enough information in it that I can find out whether I need to spend my time looking at the diff.

@Gunnex, it'd be possible to keep the original User created page with UploadWizard text and construct a semi-custom edit summary after that User created page with UploadWizard: Author: John Q. Author; Source: {{own}}; description...

Let's put it like this: "User created page with UploadWizard" is a non-information which does not need to be in there at all.