I've never had this issue come up before, but when answering this question I kept referencing the same items repeatedly. When that happens:
No, there's no recommendation for this. It's not really a problem, so no need for guidance to avoid the non-problem.
Link as many times as is useful. One style (which Wikipedia uses) is to provide a link for the first instance of a keyword in a section, then skip the link for the rest of the instances in that section. Another style (often seen in technical or user help documentation) is to link every instance of a keyword. It's a matter of taste here, since we don't impose a site style guide.
One way to generate fewer link entries at the bottom, if this is a problem for you, is to reuse the same link if you've already used it. This won't make any difference for the reader, but could make a difference for you (saving time, or help you be less self-conscious about a tower of links). You can do this by noting in the editor what the [n] after the link is, and reusing that number manually instead of using the new-link button at the top of the editor.
So, the first time you link to http://www.d20srd.org/srd/spells/harm.htm, use the new-link button. The second time you want to link to it, instead of using the button, just add it manually like so:
... this allows its [Harm][1] ability to be used...
If you forget what the number matching a URL is, you can always check at the bottom of the answer box to see what number the new-link button assigned to it originally.
Or, rather, there's another way that skips the trouble of remembering what number is for what...
If you're linking things repeatedly, you may want to replace the number (that [1]) at the bottom of your editor with a name and use that instead of numbers. This makes it easier to remember since it's the name of the thing itself, but it means you can take a shortcut linking to the item itself:
... this allows its [Harm] ability to be used...
[harm]: http://example.com
Note you didn't even have to include the second square bracket for the link! You just threw square brackets around the word itself, which saves a lot of work. But you can still do that if you want:
... And as for [that harm spell I mentioned][harm] ...
But really, no need to worry. Links are free in terms of text real estate, and handy to have nearby the relevant text.
[Harm][1] in the body and [1]: ... below, you can just have [Harm] in the body (no second [] after it) and [harm]: ... below. Makes linking to it over and over a lot easier, you'll never have to remember which number is which and won't make a link mistake. Every time you want to link to Harm, just write [Harm] and... that's it.
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Apr 27, 2015 at 4:17