From Tamosaitis v. Bechtel National, Inc. (Wash. Ct. App. July 1, 2014):

RAP [Rule of Appellate Procedure] 10.4(b) limits a respondent’s brief to no more than 50 pages. Although the respondents’ initial brief contains exactly 50 full pages, its excessive use of footnotes, 47 in all, is clearly intended to circumvent the page limits set by RAP 10.4(b). Many of these footnotes take up a third of a page or more, and contain core facts and substantive argument intended to directly support the respondents’ argument for affirming summary judgment. Had the respondents put these items in the body of their brief, the brief would have greatly exceeded the 50 page limit.

We have repeatedly told parties to make their argument in the body of their brief, not their footnotes. State v. Harris, 164 Wn. App. 377, 389 n.7, 263 P.3d 1276 (2011); State v. N.E., 70 Wn. App. 602, 606 n.3, 854 P.2d 672 (1993); State v. Johnson, 69 Wn. App. 189, 194 n.4, 847 P.2d 960 (1993). We have also rejected attempts to circumvent the page limits by trying to incorporate by reference pages from arguments made at the trial court. Diversified Wood Recycling, Inc. v. Johnson, 161 Wn. App. 859, 890, 251 P.3d 293 (2011). While the complicated nature of this case likely justified the need for over-length briefing, we have rules for seeking permission to file an over-length brief. RAP 10.4(b).

I would think that one good solution to the problem is to shift, as many (most?) courts have, to word limits. But if there are page limits, trying to circumvent them through heavy use of footnotes, especially for substantive argument, isn’t a good idea: Even if the judges won’t be annoyed, anything said in footnotes is especially likely to be skimmed or even skipped. Footnotes are sometimes useful (if local custom tolerates them), for instance for extended tangential citations that would otherwise make the text hard to read, or for responses to fairly unlikely counterarguments. But if you have something to say that you really do want judges to notice, put it in the text.