You can indeed see who has upvoted a musing.io user's question using the steem blockchain. Let's say I upvote this question (which I have) posed by @verbose-jimmy on musing.io:
You can view who upvoted your question by visiting steemit.com. Once you visited to the steemit.com you should look at comment section and tap on the question which you want to know who upvoted you.
You can indeed see who has upvoted a musing.io user's question using the steem blockchain. Let's say I upvote this question (which I have) posed by @verbose-jimmy on musing.io:
https://musing.io/q/verbose-jimmy/f3jece4sx?r=answer
I go to find the user @verbose-jimmy on steemd.com:
https://steemd.com/@verbose-jimmy
From the musing.io link anybody who upvotes the question by verbose-jimmy/f3jece4sx will be shown as:
(steemit username) upvote @verbose-jimmy/f3jece4sx.
Using the "find on page" option for the internet browser search for "verbose-jimmy/f3jece4sx". In this example what gets shown is:
holovision upvote @verbose-jimmy/f3jece4sx
You can view who upvoted your question by visiting steemit.com. Once you visited to the steemit.com you should look at comment section and tap on the question which you want to know who upvoted you.