- I think "Browser-local time" should be a preference for "Time zone" and used only if that's the chosen setting. Could be the default setting, though for new users. Disclosure: I use UTC, not local time (possible bias).
- Currently there's only a "Fill in from browser" option, that grabs the browser's time offset (that includes the current day-light saving) and stores as a setting. That setting does not follow day-light and timezone changes, therefore it's not really useful.
- I often copy the date-time, including timezone to refer to specific comments/diffs or to search for the time in the history. For these usages consistency of the comment timestamps and history timestamp is important, both should follow the wiki preference.
- Showing the relative time by default and the absolute time (wiki preference / UTC) on hover is common in messaging software and quite convenient in Flow. However, the tooltip popup solution of reddit is not so convenient imo.
- It would be a nice feature to have with a setting that enables it (could be enabled by default for new users). Note: I actually don't use it, but I know editors who have some script to do this for talk page comments.
- The user should be able to easily select and copy the absolute time. If the presentation changes on hover, there should be some padding to allow for the mouse pointer to move past the last character. Currently, in Flow the user has to stop moving the mouse precisely after the last (first) character.
- Communicating using UTC in global communities is common. There should be an option to show the time in UTC zone on hover, regardless of the wiki preference and whether relative time is shown by default.