Dangling Past Participle (edit)

[Truerenigma]

Dangling Past Participle

The past sneaks
in disguised
I'm not sure you need L2 here. I think something like "The past sneaks in/ in a poem.." is more succinct and solid.
in a pom-pommed beanie
and an IDGAF teeshirt.

Its hum is masked
in an undercurrent,
The mask and the undercurrent are probably just hurting your metaphor here. Perhaps just stick to the one metaphor here: the hum is a happy earworm. Earworms don't wear masks or have an undercurrent.
a happy earworm that bounces
with a light step and a grin.

It can’t quite meet
your eye and act
as if scar tissue
removal is minor
surgery.
Maybe cut S3 altogether.

I like the poem! S1 and S2 are light and whimsical, each with a simple metaphor. In S3 the tone changes and becomes a little more dramatic, it doesn't feel like it connects with the rest of the poem.