When importing an SVG file into Figma, text sized using pixel values renders correctly. However, any SVG text that is sized using ems (font-size: 0.8em;) is interpreted as 0.8 pixels instead of 12.8 pixels (assuming a 16px browser default font size). This makes all svg text look microscopic.
So an SVG that renders correctly in the browser, will look like this (note the microscopic text):
If I edit the svg file to convert the ems to pixels the I get the expected result:
Figma should be converting the EM values into appropriate PX font sizes (e.g 1em = 16px), not treating 1em as 1px.
I have included a sample SVG file that demonstrates the problem.