The default metadata views on ArcGIS Online feature services allow basic formatting, such as paragraphs and lists, to be included, which makes it easier for users to read the metadata. However, when a user clicks to view the full metadata, nothing is formatted and all the text for each section appears as a single mass. This has the effect of rendering the metadata meaningless (see attached image for an example of full-view output for a multi-paragraph description containing lists) for users as it is no longer in a user-friendly format. Can they parse the information if they read it slowly and several times? Sure. Should they have to go through that time-consuming effort to do it? No.
The result of poor formatting of the full metadata view means I have seen no discernible difference in requests from users in my agency for me to explain what went into developing a data set or what the data is because they find the unformatted text too difficult to read. This wastes my time twice; once writing the metadata itself as end users choose not to use it because of how hard it is to read, and second for having to repeatedly answer the same questions for multiple people because the metadata is not easily readable.
This could be addressed by either providing a version of the ArcGIS Online metadata editor as a non-editing viewer or developing translator files that enable ArcGIS Online to format the XML it is stored as in a user-friendly format for viewing. For the latter, I would suggest looking at GeoNetwork opensource to see how they were able to format full metadata views for online viewing (sure, it has its own issues, but at least it provides users a ways to view full metadata online, in a way that is easier to understand).