What utm_medium actually is
utm_medium is one of the five campaign tags a marketer types by hand into a link, and it answers a narrower question than its sibling utm_source: not which specific place sent the click, but which general category of channel that place belongs to. Typical values are cpc for paid search, email, social, referral and affiliate. Where utm_source is a name, utm_medium is a bucket, and every analytics report that groups traffic "by channel" is grouping by this field specifically.
Treat it as a closed list, not free text
utm_medium is the tag most likely to drift into inconsistency, because unlike utm_source, which is naturally constrained to the actual places you send links from, there is no obvious ceiling on how many medium values someone could invent. One person writes cpc, another writes paid-search, another writes ppc, and a channel report that should show one row for paid search shows three. The fix is picking a short fixed vocabulary before you tag anything, cpc, email, social, referral, affiliate, organic, display covers nearly every case, and writing it down somewhere the whole team can see, since a value typed once wrong tends to get copied forward by whoever builds the next link.
The pairing that actually matters
utm_medium only means something next to utm_source; neither field alone tells you much. facebook paired with cpc is a paid ad. The same facebook paired with social is an organic post. Get the pairing backwards, source in the medium field or vice versa, and the two fields stop lining up with what every other campaign in the account uses, which quietly breaks channel-level reporting even though each individual link still technically works.
Is it safe to remove?
Removing it is harmless for a visitor and changes nothing about where the link goes; it only removes the channel-category label from that click's attribution record. Since it identifies a category rather than a person, there is no privacy reason to strip it before sharing a link, only a reporting reason: whoever built the link loses the ability to group that visit by channel.