How to deal with definition lists?
I am not quite sure what you are referring to here: Off the top of my head I would think, that making description lists the way you describe is perfectly ok. Mind you, we do have a lot of detailed "rules" that have evolved over time, mostly to ensure that the the pages can be translated properly.
Could you provide a link to the page you are working on - it is often easier to comment on formatting problems in the actual context.
I use it all over the Krita manual, but here's a good example: https://userbase.kde.org/Krita/Manual/ColorManagement
This is the page that tells me not to use them: https://userbase.kde.org/Edit_Markup , it's the last bullit point of 'correcting old markup'.
I had completely forgotten about that particuar issue. I don't think this was ever meant to refer to definition lists - only to colons used on their own; or maybe it was solved with the neverland theme that we use now.
I had a look at your page. I looks fine in my browsers, so there is no reason not to continue using this markup. I'll try to find a better formulation on the Edit_Markup page to clarify (or maybe just remove the offending bullet). Thanks for pointing this out.