Regarding the first issue:
In later versions of AtoM, we added support for Markdown, which you can use to style your metadata (e.g. add bolding, italics, etc). I'm a bit surprised to see it acting on the display of the digital object file name, but I think that's what is happening here - single underscores can create italics, while double underscores can create bolding. See for example:
I tested this in our latest development branch - we've made some changes in the digital object metadata display, so I was curious to see whether the issue was resolved there. I wasn't able to recreate a formatting issue using single underscores, but double underscores did affect the filename display. I've filed a bug ticket for this issue here:
We'll try to address this for the next release, though if your institution is interested in sponsoring a fix so we can guarantee it gets addressed in 2.7, please feel free to contact Artefactual off-list and we can prepare a development estimate for you.
In the meantime, you have a couple options for workarounds to this issue.
First, you can disable Markdown entirely via the settings. See:
See the IMPORTANT note in that section of the docs - you'll need to run a few maintenance tasks after changing the setting for it to take effect. Also, be aware of one possible side effect you'll likely need to address: in 2.4, we had a custom syntax for creating hyperlinks in descriptions:
When markdown was introduced, we did away with this custom syntax, and one thing the upgrade task does is convert custom hyperlinks into Markdown ones. This means that if you've used the 2.4 custom syntax to add hyperlinks in the body of your descriptions, they will be in Markdown now - and will not render properly if you disable Markdown!
The other option is to edit the affected filenames. Fortunately, AtoM gives you an option to do this via the GUI, without having to delete and re-upload the affected digital objects. See:
Thanks for bringing this to our attention, and sorry for the inconvenience! Hopefully we can address this in the next release.
Regarding the second issue:
This is controlled by the global settings for sort order - AtoM has two different settings, one for anonymous (i.e. public, or not logged in) users, and the other for authenticated (i.e. logged in) users. This will affect the default sort order for most major entities in AtoM, including descriptions and authorities. Unfortunately, at this time we don't have a setting to control the ascending / descending sort order, but you can change the settings so that both public and authenticated users see the sort by name if desired. See:
Hope this helps!