The parenthesis character (and possibly others) are cut off, leaving them uneven, this issue is not present in other forms of text like menus or item names, but on signs it is. I presume that this is caused by the text on signs being offset and/or too large to fit.
Edit: This also seems to affect only the first line of signs
An image for context
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I could not reproduce. Are you using any resourcepacks that might change the font settings?