I recently had a client ask me why he wasn’t getting better rankings on Google. In some cases he said he didn’t appear til 5 pages in! I thought I had done a good job with the meta tag data, but now I am reading how “keywords” are mostly irrelevant now. I thought the titles were on point, but now I am seeing using commas is not a good practice. Ok. So, I asked him to send me some links of his competitors to get an idea how they were doing things. In both cases, they hardly have any meta data and hit at #1 or more often in Google, according to the client and whatever “googling” he did.
The keywords meta tag is ignored by Google and while other search engines may look at it, I don’t think any of them take it into consideration when ranking a site.
The description meta tag is useful, and Google may choose to show the text from this tag, rather than text from the page, in its search results. Good titles are also important, as you know. I don’t know where you read about not using commas, but I can see no good reason for not using them, if they help to convey the meaning of the title. Google have a very helpful SEO guide, which includes basic advice on setting up good titles and meta descriptions - and nowhere does it advise against the use of any kind of punctuation in page titles. 
More and more, the key to good ranking - especially on Google - is high quality, unique content. Anything which can be abused or manipulated to “game” the system is becoming of less and less importance.
Unfortunately, this is typical of the meaningless nonsense that we are hearing so often these days. You just need to apply a basic test of reasonableness to realise how silly it is.
The job of a search engine is to find web pages that answer the user’s query. How would the presence or absence of commas in a page’s meta data or title have the slightest effect on that? On the other hand, commas do have a definite effect on how the page’s (human) reader interprets the content. of the page. It is that which should guide you when deciding when and where to insert commas - or anything else.
In other words, apply the normal rules of punctuation, grammar and style when creating your conent. Don’t waste time looking for unverified tricks that someone believes will magically fool the search engines into giving you a better ranking.
Mike
Colin,
I’ve just re-read what I wrote yesterday. When I said:
Unfortunately, this is typical of the meaningless nonsense that we are hearing so often these days.
please don’t think I was attacking you personally. I realise it is not you who is spreading this nonsense. You are simply reporting what you read somewhere.
Mike
Thanks Technobear. I appreciate the advice.
wow, I didn’t think I was being total idiot and using zero common sense. I have always used commas where I thought they should go, but I recently heard that pipes were the best way to divide up your title content. The website seemed reputable, and the reasoning made sense - http://searchenginewatch.com/article/2154469/How-to-Write-Title-Tags-For-Search-Engine-Optimization - I understand that I am a newbie and you are a mentor, but really…Im not some babe in the woods looking for some magic beans. I was simply asking for some advice Mike.
BTW, since I am new here, I am still learning the ropes on whats ok to post vs. what is not. About 1/2 of what I originally posted was deleted by a helpful moderator. So yeah, I could see how it would come off weird. In any case, I am making progress and I have appreciated most all of the correspondence with the Sitepoint members since I began less than a year ago.
Colin, if you read my second post above (post #4), you will see that I was most definitely not calling you an idiot or accusing you of having zero common sense. On the contrary. However, if I have somehow given that impression, I apologise again.
As for the article you mentioned, it’s true that it says “Use pipes | to separate important (keyword) phrases (no commas, underscores, dashes or any other punctuation unless the keyword is written that way)”. But it doesn’t say why. It give no evidence of any kind that Google favours pipes in a title rather than other separators. I stick to my original statement that this sort of thing is meaningless nonsense.
Personally, I write my titles in a way that makes sense - and sounds natural - to my human readers. If that means using a comma as a separator, that’s what I will do. I doubt if Google would have the slightest interest in that one way or the other.
Mike