I love it.
The Irish use is because of Saint Malachy - that wasn't really his name at all but the Latinised version, Malachias, was shared with the biblical Malachi. For a Celtic saint, he has no particularly alarming associations - seems to have been a bit of a bureaucrat.
Saint Malachy was something like Maelmhaedhoc, which might not be a wise choice. There would have been a Saint Malachy's Cathedral in Ulster, but they gave the funds raised to famine relief.
I like the soft quick sounds of it as a name. Goes well with Asa that way, and with the vowel ending.
Malachi has no particular class associations for me, and not a strong Irish connection either - known to be a biblical name. Definitely would use.
I haven't heard people use the word Malarkey in real life ... ever, in Ireland or UK. Maybe an American of Biden's generation? Strikes me as a bit obsolete Hollywood Irish. Doubt anyone will make the association.
So many names begin with M that MF initials aren't rare either. Now I think of it I know a few. Never caused any problems.