We all know the log messages about over- and underfull boxes and the draft option to easily spot horizontal box problems.
Now say I am proofing a manuscript and want to spot interline, ie. vertical, spacing, problems, possibly caused by eg. font changes, \raisebox fiddling or most likely inline math with fractions, sums or integrals. I get neither log messages nor any visual help out of the box.
Is there a way to get visual clues like a black box to easily spot this if the problem is only one or two points? I suspect there is some method with luatex or microtype but I believe it to be involved and haven't found anything that is obviously helpful so far. I also played around with setting \lineskip and \lineskiplimit negative. This provides a little visual help, but I would much appreciate something more clear.
\lineskip(lines too near), the only way is to set the parameter to a very high value. The interlineskip computations are not available for the user. I'm sure it is possible with LuaTeX. – egreg Feb 07 '15 at 21:56