Doesn't look any different to me
AFAIK the font you use is irrelevant if that even makes a difference. May not look like what you expect but its the correct character. If you search the page for it only the the three examples posted will be found.
If you want to emphasize maybe larger font? Highlight the text and from the drop down box select large:H = αcL(f)^1.75
While on the subject the wiki may have something that will interest you. It supports Latex but I don't have it working at the moment because I need to install it on the server. You're familiar with that? It's all greek to me. http://en.wikipedia.org/wiki/LaTeX
I *might* be able to enable for the forum but I'll have to research it. Would that be helpful?
EDIT: Actually it looks very doable, I'm assuming you worked with this before? You have a latex editor?
From what I gather what you do is work your equation out in the editor and that will give you what to paste into the forum. I'll make a custom BBcode then all you have to do is wrap the BBcode around what you pasted and it produces an image or all kinds of things.