I think the issue is that this image resizing features depends on the syntax and it's not supported for the Markdown syntax. In short, the syntax must have the capability to support height and width parameters. In XWiki Syntax 2.1, it's: [[image:...|width="..." height="..."]] (see https://www.xwiki.org/xwiki/bin/view/Documentation/UserGuide/Features/XWikiSyntax/?syntax=2.1&section=Images).

However, to my knowledge there's no such syntax for commonmark 0.28, see https://spec.commonmark.org/0.28/#images

The only possible alternative I can think of, would be that the Markdown Renderer would generate HTML instead of markdown syntax, when a parameter is added, and re-transformed into markdown syntax when parameters are removed. It's not very nice but that's the only thing I could think of.

FTR this is a test to prove that it doesn't work:

.#-----------------------------------------------------
.input|xhtml/1.0
.# Test image with parameters
.#-----------------------------------------------------
<p><img src="imageurl" width="100" height="100"/></p>
.#-----------------------------------------------------
.expect|event/1.0
.#-----------------------------------------------------
beginDocument
beginParagraph
onImage [Typed = [false] Type = [attach] Reference = [imageurl]] [false] [[height]=[100][width]=[100]]
endParagraph
endDocument
.#-----------------------------------------------------
.expect|markdown/1.2
.#-----------------------------------------------------
![[imageurl|imageurl]]

As you can see, the markdown renderer generates ![[imageurl|imageurl]]