Selected answers from the Dumb SEO Questions G+ community.
Jim Munro: It`s not a Federal Offence but probably likely to be counter-productive.
Jason Mun: It is fine https://www.seroundtable.com/google-h1-tags-23699.html
Steve Gerencser: To follow through with markup standards it is a bad idea. H1 is not a design element, it is a structural element of your content.
Google won`t care, but it`s lazy design and may make some screen readers unhappy.
Richard Hearne: Whatever floats your boat. But what`s more important than tags used is the visual styling of content within those tags. Since Google moved to render content rather than simple text extraction (many moons ago) it`s most probable that tags matter less than visuals IMO.
Adam John Humphreys: Contextually, the placement on-page and relationship with other on page content to the query will largely determine your success. Considering that Google is run by phds that write papers in a certain writing style it`s highly probable that their algorithm is looking for relationships similar to how a paper or general paragraph is written as per English language would generally dictate. For best success with the query use synonyms and related content likely searched with your subject matter to avoid homonyms. This will reduce your bounce rate and in particular the on-topic subject matter will ascertain your place as relevant to the query.
However, before all the above make sure it`s something you would share and likely find valuable if you were someone looking at your page. One of the best reviews is as you likely know to just have someone go through it and say find something on the site itself.
In relationship to H1`s structure one can also change css font size to accomplish the same end result visually. Large text on-page is obviously dominant thing on page so unless it`s intent is to draw attention for certain focuses I would be cautious around the reason as to why someone needs a plethora of H1s.
Steven Kang: https://www.seroundtable.com/google-h1-tags-23699.html
Ash Nallawalla: I never use more than one H1. Don’t care what the standards say. We also have practical issues with CMSs where the H1 automatically becomes the Title attribute until we choose to overwrite it.
Rob Woods: not "correct" according to coding standards but minuscule as far as SEO concerns
Dave Elliott: It is allowed in html5 standards. Still don`t do it personally though.
Alan Bleiweiss: Google takes one, ignores the other. Except is the one they take the real primary topic for the page?
It is allowed in HTML5 but only properly if used when "block" and "section" code is present.
Multiple h1 tags without code blocking is not proper because the h1 represents "the single primary topic" for that page.
Multiple h1s without blocking is wasteful sloppy code.
When I see it, it is typically a sign of other sloppy code that likely confuses proper topical understanding and topical hierarchy.
So sure. You can get away with it. Why do it though? No excuse other than sloppy lazy code.
Kristine Schachinger: It`s only ok in HTML 5, but not desirable. Matt Cutts warned against it and I`ve never heard that changed, however even if that doesn`t matter it`s not good for accessibility reasons.
Christopher Fischbach: It depends on the semantic containers used. If you have just one of them, there is only one H1 supposed to be there. If there are more, you can have more H1 too. Headings are structuring elements and not for visual purposes, so it all depends on the structure you`re trying to archive.
Randy Milanovic: I asked a similar question. Ammon Johns commented unformatted docs can rank if valuable. Others believe the more prominent items gets the Love regardless of tag.
Jenny Halasz: I know we`re all talking about Google, but Bing is on record as stating they use all content for relevance, but only assign importance to the H1 (the first H1 if there are multiple) and the first H2. Makes sense to me and makes sense that Google would be similar.
Jeff Ferguson: We`ve always advised clients to keep H1 to one per page and use the HX as a way to create an outline to provide the crawlers insights into the flow of the content. Everything I`ve seen on it states that this isn`t something you`ll get penalized for, but it might make things confusing for the crawlers (similar to using the HX tags for navigation, etc.).
Dido Grigorov: I think this explains your question pretty much well :)
Dawn Anderson: I still try to stick to the one where I can despite HTML5 using containers