Whenever I used \tablenotetext on a \deluxetable, I would get an "Underfull \hbox (badness 10000)" on each line of code using \tablenotetext. This doesn't appear to cause any issues with the document, but it sufficiently annoyed me to look at it further, causing me to both find the source of the problem and the solution to it. The source of the problem is on line 5384:
2pt width0pt\relax$^{\hbox to 5pt{$#1$}}$#2\vskip1pt}}
The specific issue is using \hbox to, which is a TeX primitive and apparently doesn't play well with LaTeX (see https://tex.stackexchange.com/a/503092/200079). The solution given in that link is to use the standard LaTeX equivalent to that, \mbox. Implementing this solution to line 5384 as such solves the issue:
Whenever I used \tablenotetext on a \deluxetable, I would get an "Underfull \hbox (badness 10000)" on each line of code using \tablenotetext. This doesn't appear to cause any issues with the document, but it sufficiently annoyed me to look at it further, causing me to both find the source of the problem and the solution to it. The source of the problem is on line 5384:
2pt width0pt\relax$^{\hbox to 5pt{$#1$}}$#2\vskip1pt}}The specific issue is using \hbox to, which is a TeX primitive and apparently doesn't play well with LaTeX (see https://tex.stackexchange.com/a/503092/200079). The solution given in that link is to use the standard LaTeX equivalent to that, \mbox. Implementing this solution to line 5384 as such solves the issue:
2pt width0pt\relax$^{\makebox[5pt]{$#1$}}$#2\vskip1pt}}