It seems the LaTeX tag has been having issues lately, it does not seem to properly recognize its own tag, and does not stop at the [/eqn] but keeps going for some reason.
What seems to happen is the forum munches everything up until the last [/eqn] closing tag in the post. If this happens to be an invalid image name (to be sent to the render service the forum uses) the typesetted equation won't even come up (as in the screenshot). Otherwise it'll just display ordinary text caught in between equations. The result is you can only have one equation.. per post. It also means essentially 100% of posts having used typesetted equations, are now unreadable.
Steps to reproduce:
1. enter an equation
2. try and post that, it works
3. enter another one somewhere else
4. post again, it'll come out wrong
[eqn]ax + b[/eqn] this is not inside eqn tags [eqn]ax^2 + bx + c[/eqn]
this is not inside eqn tags
Can anyone reproduce? I don't think it's a browser issue, but Chromium here.
PS: this can also be observed in this sticky, see how roverstu's sample got mangled as well.