Steps to replicate the issue (include links if applicable):

• Set math mode to MathML
• Enter the formula \lim_{n\to +\infty}\left(1+\frac 1n\right)^n

What happens?:

Rendered as

with a lot of space around the -> and the +.

What should have happened instead?:

Rendered in SVG mode as

Software version (on Special:Version page; skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.):

When rendered on a normal line it is appropriate to have more space, so \text{let}\ {n \to +\infty} renders as

in MathML and

in SVG with more space around the arrow, but none between the + and \infty.